Patent Description:
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 <NUM>).

<CIT> describes an illumination system having a light source and a wavelength conversion layer within a light-recycling envelope. The light source is a light-emitting diode or a semiconductor laser. The light source will emit light of a first wavelength range that is transmitted through the wavelength conversion layer in order to convert a portion of the light of a first wavelength range into light of a second wavelength range. Light of both the first and second wavelength ranges will exit the light-recycling envelope through an aperture. The recycling of the light by the light-recycling envelope will enhance the output radiance and luminance of the light exiting the illumination system.

<CIT> describes a wavelength conversion material with an omni-directional reflector that is utilized to enhance the optical efficiency of an illumination system. Light guides with restricted output apertures, micro-element plates and optical elements are utilized to enhance the brightness of delivered light through light recycling. In addition, microelement plates may be used to provide control over the spatial distribution of light in terms of intensity and angle. Efficient and compact illumination systems are also disclosed.

<CIT> describes a lighting device including a wavelength converter that emits, from laser light, light having a wavelength different from a wavelength of the laser light; and a reflector surrounding the wavelength converter and including a surface of revolution that reflects the light emitted from the wavelength converter. The reflector includes, in the surface of revolution, a through-hole through which the laser light passes.

<CIT> describes a light source device including a semiconductor light-emitting device which emits coherent excitation light, and a wavelength conversion element which is spaced from the semiconductor light-emitting device.

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.

The above object is solved by an illumination device according to independent claim <NUM>. Specific embodiments are defined in the dependent claims.

The illumination device 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 <NUM>% or more and a transmittance for the laser beam at a peak wavelength is <NUM>% 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.

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.

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.

The configuration of illumination device <NUM> according to an embodiment will be described with reference to <FIG> is a diagram illustrating a configuration of illumination device <NUM> according to the embodiment. In <FIG>, the cross-section of illumination device <NUM> excluding light source <NUM> is illustrated.

As illustrated in <FIG>, illumination device <NUM> includes housing <NUM> including opening portion 10a, wavelength converting component <NUM> disposed inside housing <NUM>, optical film <NUM> disposed in opening portion 10a of housing <NUM>, and light diffusing structure <NUM> disposed on at least part of an inner wall of housing <NUM>. Illumination device <NUM> according to the present invention further includes light source <NUM>.

Housing <NUM> is an accommodator including opening portion 10a. In the present embodiment, housing <NUM> accommodates wavelength converting component <NUM>. Housing <NUM> has bottom portion <NUM> and side wall portion <NUM> erected from bottom portion <NUM>. Bottom <NUM> faces opening portion 10a. As one example, bottom portion <NUM> has a rectangular shape seen in planar view. In this case, bottom portion <NUM> is surrounded by four side wall portions <NUM>.

Housing <NUM> supports wavelength converting component <NUM> and optical film <NUM>. Specifically, the wavelength converting component is supported by bottom portion <NUM> of housing <NUM>. Optical film <NUM> is supported by the opening end portion of opening portion 10a of housing <NUM>. Wavelength converting component <NUM> and optical film <NUM> are fixed to housing <NUM> by bonding or using a latch structure or a screw.

Housing <NUM> is made of a metallic material, a resin material, or a ceramic, for example. To dissipate heat generated in wavelength converting component <NUM>, housing <NUM> may be made of a material having high thermal conductivity. Accordingly, housing <NUM> may be made of a metallic material, a resin material high thermal conductivity, or a ceramic.

Wavelength converting component <NUM> is disposed inside housing <NUM>. Specifically, wavelength converting component <NUM> is placed on bottom portion <NUM> of housing <NUM>.

Wavelength converting component <NUM> radiates wavelength-converted light having a wavelength different from that of a laser beam after the laser beam enters wavelength converting component <NUM>. In other words, wavelength converting component <NUM> converts the laser beam entering wavelength converting component <NUM> into light having a wavelength different from that of the laser beam. Specifically, wavelength converting component <NUM> 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 <NUM> does not completely absorb the laser beam and then convert it to light having a different wavelength. Rather, wavelength converting component <NUM> 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 <NUM> is converted into wavelength-converted light having a wavelength converted by wavelength converting component <NUM> and is radiated from wavelength converting component <NUM>, while another part of the laser beam entering wavelength converting component <NUM> is reflected by wavelength converting component <NUM> and is radiated from wavelength converting component <NUM> without wavelength conversion by wavelength converting component <NUM>. Specifically, wavelength converting component <NUM> has incident surface 20a which the laser beam enters. After incident surface 20a is irradiated with the laser beam, incident surface 20a 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 <NUM>, a fluorescent element containing at least one phosphor can be used, for example. In this case, wavelength converting component <NUM> (fluorescent element) emits fluorescence where the incident light serves as excitation light. As one example, wavelength converting component <NUM> 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 <NUM> (fluorescent element) is excited through irradiation with the laser beam emitted from light source <NUM> as excitation light, and radiates fluorescence having a desired color (wavelength). In other words, after the laser beam emitted from light source <NUM> enters wavelength converting component <NUM>, wavelength converting component <NUM> absorbs part of the laser beam, and is excited. Thereby, fluorescence having a predetermined color (wavelength) is radiated from wavelength converting component <NUM> as wavelength-converted light. For example, wavelength converting component <NUM> contains a phosphor which absorbs blue light having a wavelength in the range of <NUM> to <NUM> and radiates yellow green light having a wavelength from <NUM> to <NUM>. In other words, wavelength converting component <NUM> 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 <NUM> may contain several fluorescent bodies having different fluorescence peak wavelengths.

The wavelength-converted light radiated from wavelength converting component <NUM> 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 <NUM> can be somewhat weakened by the light diffusibility of wavelength converting component <NUM>, the light diffusibility of wavelength converting component <NUM> and the light absorptivity thereof are in a trade-off relation. In the present embodiment, the light absorptivity of wavelength converting component <NUM> takes precedence over the light diffusibility and a lower light diffusibility is preferred. Accordingly, wavelength converting component <NUM> 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 <NUM> may contain a light scattering material.

Examples of wavelength converting component <NUM> 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 <NUM> 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 <NUM> in the present embodiment, wavelength converting component <NUM> 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 <NUM> covers opening portion 10a of housing <NUM> including wavelength converting component <NUM> which the laser beam enters. Thereby, the wavelength-converted light obtained by wavelength conversion of the laser beam which enters wavelength converting component <NUM> and radiated by wavelength converting component <NUM> and part of the laser beam which enters wavelength converting component <NUM> reflected by wavelength converting component <NUM> without wavelength conversion by wavelength converting component <NUM> enter optical film <NUM>. 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 <NUM> enter optical film <NUM>.

Optical film <NUM> has optical properties to selectively transmit and reflect specific wavelengths of the light beams entering optical film <NUM>.

Specifically, optical film <NUM> has optical properties such that the transmittance for the wavelength-converted light radiated from wavelength converting component <NUM> is <NUM>% or more. In other words, optical film <NUM> has a high transmittance for the wavelength-converted light radiated from wavelength converting component <NUM>, and transmits most of the wavelength-converted light which is radiated from wavelength converting component <NUM> and enters optical film <NUM>. More preferably, the transmittance of optical film <NUM> for the wavelength-converted light is <NUM>% or more.

In the present embodiment, optical film <NUM> has a high transmittance not only for the wavelength-converted light radiated from wavelength converting component <NUM>, but also for light other than the wavelength-converted light outside the wavelength bandwidth of the laser beam emitted from light source <NUM>. For example, the transmittance of optical film <NUM> outside the wavelength bandwidth of the laser beam entering wavelength converting component <NUM> is preferably <NUM>% or more. This improves the light extraction efficiency of the illumination light emitted from illumination device <NUM>. More preferably, the transmittance of optical film <NUM> outside the wavelength bandwidth of the laser beam entering wavelength converting component <NUM> is <NUM>% or more. In other words, optical film <NUM> is preferably transparent for the light having a wavelength outside the wavelength bandwidth of the laser beam entering wavelength converting component <NUM>.

Optical film <NUM> has optical properties so as to reflect part of the laser beam entering optical film <NUM> and transmit another part of the laser beam. In other words, optical film <NUM> has both of an optical property to reflect the laser beam emitted from light source <NUM> and an optical property to transmit the laser beam emitted from light source <NUM>. As one example, the transmittance of optical film <NUM> for the light in the wavelength bandwidth of the laser beam emitted from light source <NUM> is <NUM>% to <NUM>%.

Furthermore, optical film <NUM> has optical properties such that the transmittance for the laser beam entering wavelength converting component <NUM> at the peak wavelength is <NUM>% or less of the transmittance for the wavelength-converted light at the peak wavelength, which is radiated from wavelength converting component <NUM>.

In the present embodiment, the laser beam emitted from light source <NUM> is blue light having a wavelength of <NUM> to <NUM> (peak wavelength: <NUM>), and the wavelength-converted light radiated from wavelength converting component <NUM> is yellow green light having a wavelength of <NUM> to <NUM> (peak wavelength: <NUM>). Thus, as its optical properties, optical film <NUM> has the transmission spectrum (transmittance distribution) shown in <FIG> as one example.

Specifically, as illustrated in <FIG>, the transmittance of optical film <NUM> for the wavelength-converted light (yellow green light) in the wavelength bandwidth of <NUM> to <NUM> is <NUM>% or more, and optical film <NUM> has a high transmittance for the wavelength-converted light.

As shown in <FIG>, the transmittance of optical film <NUM> for the laser beam (blue light) in the wavelength bandwidth of <NUM> to <NUM> is <NUM>% to <NUM>% and the transmittance of optical film <NUM> for the laser beam at the peak wavelength (<NUM>) is <NUM>%. In other words, the half or more of the laser beam entering optical film <NUM> is transmitted and the half or less of the laser beam entering optical film <NUM> is reflected. Part of the laser beam entering optical film <NUM> is absorbed by optical film <NUM>, generating heat.

Furthermore, in <FIG>, the transmittance of optical film <NUM> at the peak wavelength (<NUM>) of the wavelength-converted light is <NUM>% and that at the peak wavelength (<NUM>) of the laser beam is <NUM>%. Thus, the proportion of the transmittance (<NUM>%) at the peak wavelength of the laser beam to the transmittance (<NUM>%) at the peak wavelength of the wavelength-converted light is <NUM>. <NUM> = <NUM>%.

Optical film <NUM> 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 <NUM> has a shape of a film, a sheet, or a plate as one example, and can have any other shape.

As illustrated in <FIG>, light diffusing structure <NUM> is disposed on the inner wall of housing <NUM>. According to the invention, light diffusing structure <NUM> is disposed on the inner surface of bottom portion <NUM> and the inner surface of side wall portion <NUM> of housing <NUM>. In the present embodiment, light diffusing structure <NUM> is disposed across the entire inner surface of housing <NUM>.

Light diffusing structure <NUM> diffusely reflects the laser beam reflected by at least optical film <NUM>. Specifically, the laser beam reflected by optical film <NUM> is diffused through scattering reflection by light diffusing structure <NUM>. Although light diffusing structure <NUM> is disposed to diffuse the laser beam having high directivity reflected by mainly optical film <NUM>, 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 <NUM> in the entire wavelength band in the visible light region may be <NUM>%, the reflectance does not always need to be <NUM>%, and may be at least <NUM>% or more. Of the light beam which enters light diffusing structure <NUM>, part of the light beam not reflected by light diffusing structure <NUM> is absorbed in light diffusing structure <NUM> or housing <NUM> to generate heat, and the heat is conducted. Light diffusing structure <NUM> may diffusely reflect only the laser beam reflected by optical film <NUM>.

Light diffusing structure <NUM> to be used can be a light diffusion film including aggregates of a fine light scattering material. Here, with reference to <FIG>, a detailed configuration of light diffusing structure <NUM> will be described. <FIG> is an enlarged cross-sectional view of region III surrounded by the dashed line in <FIG>.

As illustrated in <FIG>, light diffusing structure <NUM> is a light diffusion film including light scattering material <NUM> dispersed in resin <NUM>, and is disposed on the inner wall of housing <NUM>. Such a light diffusion film to be used can be a resin film including light diffusing nanoparticles as light scattering material <NUM> dispersed in a binder resin such as a polycarbonate or acrylic resin as resin <NUM>. Specifically, a white resin film including white nanoparticles as light scattering material <NUM> (light diffusing nanoparticles) can be used. Such a light diffusing structure <NUM> can be disposed as a light diffusion coating. For example, the light diffusion coating can be disposed on the inner wall surface of housing <NUM> by applying a dispersion of an infinite number of light scattering material <NUM> dispersed in a binder resin solution onto the inner wall surface of housing <NUM>, and curing the coating.

As light diffusing structure 40A illustrated in <FIG>, a transparent inorganic filler may be used as light scattering material 41A, 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>, part of light scattering material 41A may be exposed from resin <NUM>, and light scattering material 41A may not be exposed. In <FIG>, light scattering material <NUM> may be exposed from resin <NUM>.

Although light diffusing structures <NUM> and 40A each are separately disposed from housing <NUM> in the present embodiment, light diffusing structures <NUM> and 40A each may be integrally formed with housing <NUM>. In this case, housing <NUM> is formed using the same material as those for light diffusing structures <NUM> and 40A.

As illustrated in <FIG>, light diffusing structure 40B may be a convexo-concave structure disposed on the inner wall of housing <NUM>, rather than aggregates of light scattering material <NUM> or 40A. In other words, the laser beam reflected by optical film <NUM> may be diffusely reflected according to the shape of the convexo-concave structure. The convexo-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 convexo-concave surface having a surface roughness Ra (arithmetic average roughness) of <NUM> or more. Thus, the laser beam reflected by optical film <NUM> 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 <NUM> as illustrated in <FIG>, or may be part of housing <NUM>. In other words, a convexo-concave structure may be formed on the surface of housing <NUM>.

Light diffusing structures <NUM> and 40A may be formed across the entire surface of housing <NUM>, or may be formed on part thereof. Light diffusing structures <NUM> and 40A may partially include a different structure. Desired properties of illumination device <NUM> can be controlled according to the proportion of the area where light diffusing structure <NUM> or 40A is formed or the proportion of a different structure included in light diffusing structure <NUM> or 40A. For example, the light extraction efficiency and color temperature of the illumination light emitted from illumination device <NUM> can be controlled according to the proportion of the formation area.

Light diffusing structure <NUM> 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 <NUM> can be controlled by controlling the reflectance of light diffusing structure <NUM>.

Light source <NUM> is a laser beam source which emits a laser beam. For example, light source <NUM> includes a semiconductor laser which emits a laser beam. In the present embodiment, the laser beam emitted from light source <NUM> is blue light. Specifically, the laser beam emitted from light source <NUM> is light having a peak wavelength of <NUM> and having a wavelength bandwidth of <NUM> to <NUM>, for example.

Light source <NUM> is disposed outside housing <NUM>. Light source <NUM> is disposed such that the laser beam enters wavelength converting component <NUM>. In the present embodiment, light source <NUM> is disposed such that the laser beam emitted from light source <NUM> enters wavelength converting component <NUM> with an inclination to the surface thereof.

Specifically, through hole 10b is disposed on side wall portion <NUM> of housing <NUM>, and the laser beam is emitted from light source <NUM>, and enters wavelength converting component <NUM> through hole 10b.

To control the orientation of the laser beam emitted from light source <NUM> 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 <NUM> and wavelength converting component <NUM>. Light source <NUM> may be disposed inside housing <NUM> rather than outside housing <NUM>. In this case, through hole 10b of housing <NUM> is unnecessary.

Next, the optical action of illumination device <NUM> according to the present embodiment will be described with reference to <FIG> is a diagram illustrating trajectories of light beams in illumination device <NUM> according to the embodiment.

As illustrated in <FIG>, after laser beam LB1 is emitted from light source <NUM>, laser beam LB1 (the solid bold line in <FIG>) enters the surface of wavelength converting component <NUM> from an oblique direction. When laser beam LB1 enters wavelength converting component <NUM>, part of laser beam LB1 is absorbed in wavelength converting component <NUM> to be subjected to wavelength conversion. Wavelength-converted light LC2 (the dashed line in <FIG>) having a wavelength different from that of laser beam LB1 is radiated from wavelength converting component <NUM>, and another part of laser beam LB1 is reflected by wavelength converting component <NUM> without being absorbed in wavelength converting component <NUM> to be converted into laser beam LB2 (the solid semi-bold line in <FIG>).

As a result, wavelength-converted light LC2 and the reflected laser beam LB2 are radiated from wavelength converting component <NUM>. At this time, wavelength-converted light LC2 is radiated in all the directions. Laser beam LB2 reflected by wavelength converting component <NUM> is radiated while maintaining directivity.

Wavelength-converted light LC2 and laser beam LB2 radiated from wavelength converting component <NUM> travel to optical film <NUM>, and enter optical film <NUM>.

At this time, optical film <NUM> has a transmittance of <NUM>% or more for the wavelength-converted light generated in wavelength converting component <NUM>. For this reason, most of wavelength-converted light LC2 which enters optical film <NUM> transmits through optical film <NUM>, and is radiated to the outside of housing <NUM>.

Optical film <NUM> has both an optical property to reflect the laser beam emitted from light source <NUM> and an optical property to transmit the laser beam emitted from light source <NUM>. For this reason, part of laser beam LB2 which enters optical film <NUM> travels straight and transmits through optical film <NUM>, and is radiated to the outside of housing <NUM> as laser beam LB3 (the solid thin line in an upper portion of <FIG>), and another part of laser beam LB2 is reflected by optical film <NUM>, and travels toward the lower portion of housing <NUM> as laser beam LB4 (the solid thin line in a lower portion of <FIG>). In other words, laser beam LB2 which enters optical film <NUM> is separated into laser beam LB3 (light traveling straight) and laser beam LB4 (reflected light) by optical film <NUM>.

Laser beam LB4, which is reflected by optical film <NUM> and travels to the lower portion of housing <NUM>, enters light diffusing structure <NUM> disposed on the inner wall of housing <NUM>. Light diffusing structure <NUM> has a function to diffusely reflect at least the laser beam emitted from light source <NUM>. Thus, laser beam LB4 which enters light diffusing structure <NUM> is diffusely reflected by light diffusing structure <NUM>, and is radiated from light diffusing structure <NUM> as diffused light LD5 (the dashed-and-dotted line in <FIG>) in an isotropic-scattering manner.

Diffused light LD5 diffusely reflected by light diffusing structure <NUM> travels toward the upper portion of housing <NUM> inside housing <NUM>. In other words, diffused light LD5 travels toward optical film <NUM>, and enters optical film <NUM>.

Here, diffused light LD5 has the same wavelength as that of the laser beam emitted from light source <NUM>. As described above, optical film <NUM> has both an optical property to reflect the laser beam emitted from light source <NUM> and an optical property to transmit the laser beam emitted from light source <NUM>. Accordingly, part of diffused light LD5 which enters optical film <NUM> travels straight and transmits through optical film <NUM>, and is radiated to the outside of housing <NUM>, while another part of diffused light LD5 which enters optical film <NUM> is reflected by optical film <NUM> to return to the inside of housing <NUM>, and travels toward the lower portion of housing <NUM>.

The diffused light of diffused light LD5, which is reflected by optical film <NUM> and travels inside housing <NUM> toward the lower portion thereof, is again diffusely reflected by light diffusing structure <NUM> and reenters optical film <NUM>. In other words, diffused light LD5 is repeatedly subjected to reflection by and transmission through optical film <NUM> and diffuse reflection by light diffusing structure <NUM>.

As a result, laser beam LB4, which is reflected by wavelength converting component <NUM> and then by optical film <NUM>, is finally converted to diffused light by light diffusing structure <NUM>. In other words, laser beam LB4 is completely converted to diffused light, transmits through optical film <NUM>, and is radiated to the outside of housing <NUM>. For this reason, irrespective of the absorptivity of wavelength converting component <NUM>, light diffusibility for laser beam LB1 emitted from light source <NUM> can be ensured.

At this time, as a result of laser beam LB4 being repeatedly subjected to reflection by and transmission through optical film <NUM> and diffuse reflection by light diffusing structure <NUM>, laser beam LB3 can have a sufficiently small light quantity to the light quantity extracted as the diffused light to the outside of housing <NUM>. Thus, color unevenness of the irradiation pattern of the mixed light can be reduced.

Thus, in illumination device <NUM> according to the present embodiment, the laser beam having high directivity can have diffusibility because of optical film <NUM> and light diffusing structure <NUM> even if the light diffusibility is not imparted to wavelength converting component <NUM>. The wavelength-converted light generated by wavelength converting component <NUM> using the laser beam as excitation light has diffusibility. In other words, the laser beam radiated from opening portion 10a of housing <NUM> 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 <NUM> can be reduced.

Furthermore, in illumination device <NUM> according to the present embodiment, formation of projections and depressions on the surface of wavelength converting component <NUM> or mixing of a filler having light scattering properties in wavelength converting component <NUM> is unnecessary for the purpose of enhancing the light diffusibility of wavelength converting component <NUM>, and therefore the absorptivity of the laser beam in wavelength converting component <NUM> 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 <NUM> 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 <NUM>, 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 <NUM> 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 <NUM> according to the embodiment will be described with reference to <FIG> and <FIG>. <FIG> is a perspective view of illumination device 1A according to an example of application. <FIG> is a partial cross-sectional view of illumination device 1A. <FIG> illustrates a state where optical film <NUM> is removed.

As illustrated in <FIG> and <FIG>, illumination device 1A according to the present modification further includes base <NUM>, lens <NUM>, and reflective component <NUM>.

Base <NUM> is the main body including housing <NUM> and light source <NUM>. Housing <NUM> is placed on the top surface of base <NUM>. Light source <NUM> is accommodated inside base <NUM>.

Base <NUM> also functions as a heat sink to dissipate heat generated in wavelength converting component <NUM> through light source <NUM> and housing <NUM>. Accordingly, base <NUM> 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 <NUM> is a collimator lens. The laser beam radially emitted from light source <NUM> is converted to parallel light having a predetermined beam diameter by lens <NUM>.

Reflective component <NUM> reflects the laser beam emitted from light source <NUM>, and emits the reflected laser beam to wavelength converting component <NUM> disposed inside housing <NUM>. Specifically, reflective component <NUM> reflects the laser beam collimated by lens <NUM>. Reflective component <NUM> is attached to part of base <NUM>.

Although light source <NUM> is held by base <NUM> in the present modification, light source <NUM> may be disposed outside base <NUM> and the laser beam may be transmitted from light source <NUM> through an optical fiber to cause the laser beam to enter reflective component <NUM>. In this case, an end portion of the optical fiber is disposed at the position of light source <NUM> in <FIG>.

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 <NUM> 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 <NUM> is caused to enter wavelength converting component <NUM> in the embodiments above, irradiation of wavelength converting component <NUM> with the laser beam can be performed by any other method. For example, as illustrated in <FIG>, the laser beam emitted from light source <NUM> may be transmitted through optical fiber <NUM>, and the laser beam emitted from one end portion of optical fiber <NUM> may be emitted to wavelength converting component <NUM>. In this case, in <FIG>, the light emitting portion (one end portion of optical fiber <NUM>) is disposed inside housing <NUM>. The light emitting portion may be disposed outside housing <NUM>.

Although light diffusing structure <NUM> including aggregates of a light scattering material (<FIG>) or light diffusing structure 40A having a convexo-concave structure on its surface (<FIG>) is disposed on the inner wall of housing <NUM> 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>, light diffusing structure 40C may have a concave surface defined by a curved surface of the inner wall (inner wall surface) of housing <NUM>. In this case, light diffusing structure 40C may have a smooth concave surface defined by a curved inner wall surface of housing <NUM>, or may include the aggregates of a light scattering material illustrated in <FIG> or the convexo-concave structure illustrated in <FIG> on the surface of the concave surface.

Claim 1:
An illumination device (<NUM>, 1A), comprising:
a housing (<NUM>) including an opening portion (10a);
a light source (<NUM>) which emits a laser beam (LB1);
a wavelength converting component (<NUM>) which is disposed inside the housing (<NUM>) and radiates wavelength-converted light (LC2) after the laser beam (LB1) enters the wavelength converting component (<NUM>), the wavelength-converted light (LC2) having a different wavelength from a wavelength of the laser beam (LB1);
an optical film (<NUM>) which covers the opening portion (10a), the optical film (<NUM>) having optical properties such that a transmittance for the wavelength-converted light (LC2) is <NUM>% or more and a transmittance for the laser beam (LB1) at a peak wavelength is <NUM>% or less of a transmittance for the wavelength-converted light (LC2) at a peak wavelength,
wherein the optical film (<NUM>) has optical properties so as to reflect part of the laser beam (LB1) entering the optical film (<NUM>) and transmit another part of the laser beam (LB1), wherein half or more of the laser beam (LB1) entering the optical film (<NUM>) is transmitted and half or less of the laser beam (LB1) entering the optical film (<NUM>) is reflected; and
a light diffusing structure (<NUM>, 40A, 40B, 40C) which is disposed on at least part of an inner wall of the housing (<NUM>) and diffusely reflects a part of the laser beam (LB1) that is reflected by the wavelength converting component (<NUM>) and is further reflected by the optical film (<NUM>),
wherein the light diffusing structure (<NUM>, 40A, 40B, 40C) is disposed on an inner surface of a bottom portion (<NUM>) of the housing (<NUM>) and an inner surface of a side wall portion (<NUM>) of the housing (<NUM>).