Lighting device

Abstract

A lighting device comprises a housing, a light source, a wavelength conversion member, a wavelength separation filter, and a lens optical system. The housing has a first opening. The light source emits excitation light. The wavelength conversion member is located inside the housing. The excitation light from the light source is incident on the wavelength conversion member. The wavelength conversion member emits, on the basis of the excitation light, fluorescence having a spectrum different from that of the excitation light. The wavelength separation filter is located inside the housing, guides the excitation light from the light source to the wavelength conversion member, and guides the fluorescence from the wavelength conversion member to the first opening. The lens optical system comprises one or more first lenses. The first lens is located between the wavelength separation filter and the wavelength conversion member inside the housing, focuses the excitation light on the wavelength conversion member, and transmits the fluorescence from the wavelength conversion member toward an effective surface of the wavelength separation filter.

Description

lighting equipment CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2022-108911 (filed July 6, 2022), the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to a lighting device.

[0003] 2. Description of the Related Art Light-emitting devices including a light source, a beam splitter, and a wavelength conversion member have been proposed (for example, see Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2014-203852

[0005] A lighting device is disclosed.

[0006] In one embodiment, the lighting device includes a housing, a light source, a wavelength conversion member, a wavelength separation filter, and a lens optical system. The housing has a first opening. The light source emits excitation light. The wavelength conversion member is located inside the housing. The excitation light from the light source is incident on the wavelength conversion member. The wavelength conversion member emits fluorescence having a spectrum different from that of the excitation light based on the excitation light. The wavelength separation filter is located inside the housing and guides the excitation light from the light source to the wavelength conversion member and guides the fluorescence from the wavelength conversion member to the first opening. The lens optical system includes one or more first lenses. The first lens is located inside the housing between the wavelength separation filter and the wavelength conversion member and focuses the excitation light on the wavelength conversion member and transmits the fluorescence from the wavelength conversion member toward the effective surface of the wavelength separation filter.

[0007] FIG. 1 is a schematic cross-sectional view of an example of the configuration of an illumination device according to a first embodiment; FIG. 2 is a cross-sectional view schematically showing an example of a light path in the illumination device according to the first embodiment; FIG. 3 is an enlarged cross-sectional view showing an enlarged configuration of a portion of the illumination device of FIG. 1; FIG. 4 is a graph showing an example of the spectral transmittance of a wavelength separation filter; FIG. 5 is a diagram schematically showing a first example of the configuration of a filter holder; FIG. 6 is a diagram schematically showing a second example of the configuration of a filter holder; FIG. 7 is a cross-sectional view schematically showing an example of the configuration of an illumination device according to a second embodiment; FIG. 8 is a diagram schematically showing an example of the configuration of an optical system of an illumination device according to a third embodiment; and FIG. 9 is a diagram schematically showing an example of the configuration of an optical system of an illumination device according to a fourth embodiment.

[0008] The inventor has created a technology that enables a lighting device to emit illumination light with higher efficiency. Hereinafter, lighting devices 1 according to first to fourth embodiments will be described with reference to the drawings.

[0009] <1. First embodiment> <1-1. Schematic configuration of lighting device 1> Fig. 1 is a cross-sectional view schematically showing an example of the configuration of lighting device 1 according to the first embodiment. Fig. 2 is a cross-sectional view schematically showing an example of a light path in lighting device 1 according to the first embodiment. Fig. 3 is an enlarged cross-sectional view showing an enlarged configuration of a portion of lighting device 1 in Fig. 1. Figs. 1 to 3 show an example of the configuration of lighting device 1 in a cross section including an optical axis AX1, which will be described later.

[0010] 2, the lighting device 1 is a device that emits fluorescent light L1 as illumination light into an illumination space S1. The illumination space S1 is, for example, an interior space of a building. The lighting device 1 is disposed, for example, on the ceiling of the illumination space S1.

[0011] The lighting device 1 includes a light source 2, a wavelength conversion member 3, a wavelength separation filter 4, a lens optical system 5, and a housing 6. In the following, an example of each component will first be outlined, and then described in detail.

[0012] The housing 6 houses the light source 2, the wavelength conversion member 3, the wavelength separation filter 4, and the lens optical system 5. The housing 6 has a first opening (hereinafter also referred to as an irradiation opening) 6a. Fluorescence L1 as illumination light is emitted from the irradiation opening 6a into the illumination space S1.

[0013] The light source 2 has an emission section (e.g., an emission surface) 21 that emits excitation light L0. The excitation light L0 may be light having a peak in the wavelength range of 380 nm to 415 nm, for example. As a specific example, the excitation light L0 may be purple light having a peak near 405 nm. Note that the excitation light L0 is not necessarily limited to purple light, and may be blue light having a peak near 450 nm, for example.

[0014] The excitation light L0 from the light source 2 is incident on the wavelength separation filter 4. In the example of FIG. 2 , an example of the outer contour of the excitation light L0 is schematically shown by a dashed line. The wavelength separation filter 4 is located inside the housing 6 and guides the excitation light L0 to the wavelength conversion member 3. In the examples of FIGS. 1 and 2 , the wavelength conversion member 3 and the wavelength separation filter 4 are aligned along a direction (corresponding to a first direction) along an optical axis AX1 described below, and the light source 2 and the wavelength separation filter 4 are aligned along a second direction intersecting the first direction. In this case, the wavelength separation filter 4 reflects the excitation light L0 from the light source 2 toward the wavelength conversion member 3.

[0015] The lens optical system 5 includes one or more first lenses 51 located between the wavelength separation filter 4 and the wavelength conversion member 3 inside the housing 6. In the example of FIGS. 1 and 2 , a first-A lens 51A and a first-B lens 51B are shown as the first lenses 51. The first-A lens 51A is located closer to the wavelength conversion member 3 than the first-B lens 51B. The excitation light L0 reflected by the wavelength separation filter 4 passes through the first-B lens 51B and the first-A lens 51A in this order and enters the wavelength conversion member 3. The first-A lens 51A and the first-B lens 51B focus the excitation light L0 from the wavelength separation filter 4 onto the wavelength conversion member 3. Note that the number of first lenses 51 between the wavelength separation filter 4 and the wavelength conversion member 3 is not limited to two, and may be one, or three or more. Hereinafter, the optical axis of the first-A lens 51A will also be referred to as the optical axis AX1, and the direction along the optical axis AX1 will also be referred to as the optical axis direction.

[0016] The wavelength conversion member 3 has, for example, a surface 3a, a surface 3b, and a side surface 3c. The surface 3b is the surface of the wavelength conversion member 3 facing the first lens 51. The surface 3a is the surface of the wavelength conversion member 3 opposite to the surface 3b. The side surface 3c is a side surface connecting the periphery of the surface 3a and the periphery of the surface 3b of the wavelength conversion member 3. The wavelength conversion member 3 may have a plate-like shape. In other words, the surfaces 3a and 3b of the wavelength conversion member 3 may be substantially flat surfaces and substantially parallel to each other. The wavelength conversion member 3 is positioned with its thickness direction aligned with the optical axis direction. In the example of FIGS. 1 and 2 , the surface 3a of the wavelength conversion member 3 is covered by an attachment member 64 of the housing 6. The attachment member 64 will be described in detail later.

[0017] The excitation light L0 transmitted through the first lens 51 is incident on the surface 3b of the wavelength conversion member 3. The wavelength conversion member 3 contains a phosphor, and emits fluorescence L1 having a spectrum different from that of the excitation light L0 based on the incident excitation light L0. For example, the peak wavelength of the fluorescence L1 is longer than the peak wavelength of the excitation light L0, and the fluorescence L1 is visible light. The spread angle of the fluorescence L1 emitted from the wavelength conversion member 3 is large, for example, about 180 degrees.

[0018] At least a portion of the fluorescence L1 from the wavelength conversion member 3 passes through the first lens 51 (here, the firstA lens 51A and the firstB lens 51B) and enters the wavelength separation filter 4. In FIG. 2, an example of the outer contour of the fluorescence L1 entering the firstA lens 51A is schematically shown by a two-dot chain line. The firstA lens 51A and the firstB lens 51B transmit the fluorescence L1 toward the effective surface of the wavelength separation filter 4. The effective surface here refers to the range in which the filtering function of the wavelength separation filter 4 can be realized. The wavelength separation filter 4 guides the fluorescence L1 to the irradiation opening 6a. In the example of FIGS. 1 and 2, the wavelength conversion member 3, the wavelength separation filter 4, and the irradiation opening 6a are aligned in the optical axis direction. In this case, the wavelength separation filter 4 transmits the fluorescence L1 toward the irradiation opening 6a.

[0019] 2, the lens optical system 5 may further include a second lens 52 located between the wavelength separation filter 4 and the illumination opening 6a inside the housing 6. The first lens 51 and the second lens 52 are aligned on the optical axis. In this case, the fluorescence L1 from the wavelength separation filter 4 passes through the second lens 52 and is emitted into the illumination space S1 through the illumination opening 6a.

[0020] As described above, in the lighting device 1, one or more first lenses 51 are positioned between the wavelength separation filter 4 and the wavelength conversion member 3. The first lenses 51 can narrow the fluorescence L1 traveling from the wavelength conversion member 3 at a large divergence angle. In other words, the first lenses 51 can reduce the divergence angle of the fluorescence L1. This allows more fluorescence L1 to be guided to the wavelength separation filter 4 without increasing the size of the wavelength separation filter 4. In other words, more of the fluorescence L1 emitted by the wavelength conversion member 3 can be guided to the irradiation opening 6a through the wavelength separation filter 4. Conversely, the proportion of the fluorescence L1 not directed toward the irradiation opening 6a can be reduced among the total fluorescence L1 emitted by the wavelength conversion member 3. This allows the lighting device 1 to emit the fluorescence L1 into the illumination space S1 with higher efficiency.

[0021] Furthermore, by disposing the first-A lens 51A close to the wavelength conversion member 3, even more of the fluorescence L1 from the wavelength conversion member 3 can be incident on the first-A lens 51A. This allows the lighting device 1 to emit the fluorescence L1 into the illumination space S1 with even higher efficiency.

[0022] Moreover, according to the lighting device 1, the excitation light L0 from the wavelength separation filter 4 passes through one or more first lenses 51 and enters the wavelength conversion member 3. Therefore, even if the distance between the wavelength conversion member 3 and the first-A lens 51A is narrow, the excitation light L0 can be appropriately incident on the relatively wide surface 3b of the wavelength conversion member 3. Since the wavelength conversion member 3 can generate fluorescence L1 over a wider range, it can generate a greater amount of fluorescence L1. Consequently, the lighting device 1 can emit a greater amount of fluorescence L1 into the illumination space S1.

[0023] Hereinafter, a more specific example of each component of the lighting device 1 will be described, roughly divided into the optical system and the housing 6. First, the optical system will be described, and then the housing 6 will be described.

[0024] <1-2. Optical System> <1-2-1. Light Source 2> The light source 2 may include, for example, a semiconductor laser element such as a laser diode (LD), a vertical cavity surface emitting laser (VCSEL), a light emitting diode (LED), or a super luminescent diode (SLD). The emission unit 21 of the light source 2 may be the emission end of the light emitting element. For example, a gallium nitride (GaN) semiconductor laser that emits 405 nm violet laser light as excitation light L0 may be used as the light emitting element.

[0025] Alternatively, the light source 2 may further include a light-guiding member such as a fiber and a rod lens in addition to the light-emitting element. The fiber includes a linear core and cladding. The cladding has a lower refractive index than the core and covers the core. The excitation light L0 can pass through the core while being totally reflected at the boundary between the core and the cladding. The rod lens has, for example, a cylindrical shape. The excitation light L0 can pass through the rod lens while being totally reflected at the side of the rod lens. The incident end of such a light-guiding member corresponds to a first end face located at the longitudinal end of the fiber or a first end face located at the end of the rod lens, and the exit end of the light-guiding member corresponds to a second end face opposite the first end face of the fiber or a second end face opposite the first end face of the rod lens. The excitation light L0 from the light-emitting element enters the incident end of the light-guiding member, travels through the light-guiding member, and exits from the exit end of the light-guiding member. In this case, the exit section 21 of the light source 2 corresponds to the exit end of the light-guiding member.

[0026] The light source 2 may emit linearly polarized excitation light L0. The polarization of the excitation light L0 may be, for example, s-polarized with respect to the incident surface of the wavelength separation filter 4. Furthermore, various lenses may be positioned between the light source 2 and the wavelength separation filter 4.

[0027] <1-2-2. Wavelength separation filter 4> As described above, the wavelength separation filter 4 guides the excitation light L0 from the light source 2 to the wavelength conversion member 3, and guides the fluorescence L1 from the wavelength conversion member 3 to the irradiation opening 6a. In the example of Fig. 2, the wavelength separation filter 4 reflects the excitation light L0 toward the wavelength conversion member 3 and transmits the fluorescence L1 toward the irradiation opening 6a. The wavelength separation filter 4 is also called, for example, a dichroic mirror or a dichroic film.

[0028] As shown in FIGS. 1 and 2 , the wavelength separation filter 4 may include a substrate 41 and a dielectric multilayer film 42. The substrate 41 is a transparent member containing at least one of glass such as optical glass and resin such as acrylic resin, and may have a flat plate shape. The dielectric multilayer film 42 is located on the first surface 4 a or the second surface 4 b of the substrate 41, for example. The dielectric multilayer film 42 has a structure in which thin dielectric films are repeatedly stacked, for example. The dielectric may be, for example, silicon oxide (SiO ２ ), titanium oxide (TiO ２ ), aluminum oxide (Al ２ O ３ ), zirconium oxide (ZrO ２ ), tantalum oxide (Ta ２ O ５ ) and niobium oxide (Nb ２ O ３ ) is used. For example, by appropriately setting the thicknesses of the multiple dielectric thin films that make up the dielectric multilayer film 42, a spectral transmittance that reflects the excitation light L0 and transmits the fluorescence L1 in the dielectric multilayer film 42 can be achieved. The wavelength separation filter 4 has a dielectric multilayer film that separates wavelengths on the first surface 4a, and may have an anti-reflection film on the second surface 4b. This reduces the risk of a decrease in the amount of light due to absorption by the substrate 41 of the wavelength separation filter 4, compared to when a dielectric multilayer film is located on the second surface 4b.

[0029] FIG. 4 is a graph showing an example of the spectral transmittance of the wavelength separation filter 4. FIG. 4 shows the transmittance Ts of the wavelength separation filter 4 for s-polarized light and the transmittance Tn of the wavelength separation filter 4 for unpolarized light. Here, the polarization state of the excitation light L0 is s-polarized, and its wavelength is 405 nm. In the example of FIG. 4 , the transmittance Ts for the excitation light L0 is almost zero, so the excitation light L0 is hardly transmitted through the wavelength separation filter 4. For simplicity's sake, if the absorption rate of the wavelength separation filter 4 is assumed to be almost zero, the excitation light L0 is reflected by the wavelength separation filter 4 with almost 100% reflectance. On the other hand, the polarization state of the fluorescence L1 is unpolarized. In the example of FIG. 4 , the transmittance Tn in the wavelength range of 450 nm or more is almost 100%, so that the fluorescence L1 having a wavelength of 450 nm or more is transmitted through the wavelength separation filter 4 with almost 100% transmittance.

[0030] The reflectance of the wavelength separation filter 4 for the excitation light L0 (for example, the reflectance when the wavelength is 420 nm or shorter) may be, for example, 80% or more, 90% or more, or 95% or more. The transmittance Tn of the wavelength separation filter 4 for the fluorescence L1 (for example, the transmittance Tn when the wavelength is 450 nm or longer) may be, for example, 80% or more, 90% or more, or 95% or more.

[0031] As described above, the wavelength separation filter 4 reflects the excitation light L0 and transmits the fluorescence L1. In the example of FIG. 1 , the wavelength separation filter 4 is positioned such that its thickness direction intersects with the optical axis AX1 of the first lens 51 at an angle close to 45 degrees. Also, in the example of FIG. 1 , the emission direction of the excitation light L0 from the light source 2 intersects with the surface of the dielectric multilayer film 42 of the wavelength separation filter 4 at an angle close to 45 degrees. This allows the excitation light L0 from the light source 2 to be reflected toward the wavelength conversion member 3. A specific example of the orientation of the wavelength separation filter 4 and the emission direction of the excitation light L0 will be described later.

[0032] 1-2-3. Lens Optical System 5 (First Lens 51) As shown in FIG. 1 , the first lens 51 (here, the first-A lens 51A and the first-B lens 51B) may be, for example, a biconvex lens. The first lens 51 is formed of a material containing at least one of glass, such as optical glass, and resin, such as acrylic resin. The first-A lens 51A and the first-B lens 51B focus the excitation light L0 from the wavelength separation filter 4 onto the wavelength conversion member 3. In the example of FIG. 2 , the degree of divergence of the excitation light L0 decreases each time the excitation light L0 passes through the first-B lens 51B and the first-A lens 51A. In the example of FIG. 2 , the size of the cross section of the excitation light L0 that has passed through the first-B lens 51B, perpendicular to the optical axis AX1, decreases as the excitation light L0 travels toward the wavelength conversion member 3. In other words, the excitation light L0 travels toward the wavelength conversion member 3 while narrowing.

[0033] The first-A lens 51A and the first-B lens 51B may cause the excitation light L0 to be incident on a part of the surface 3b of the wavelength conversion member 3, or may cause the excitation light L0 to be incident on the entire surface 3b of the wavelength conversion member 3. The wavelength conversion member 3 emits fluorescence L1 based on the excitation light L0.

[0034] The first-A lens 51A and the first-B lens 51B transmit the fluorescence L1 from the wavelength conversion member 3 toward the effective surface of the wavelength separation filter 4. In the example of FIG. 1 , the degree of spread of the fluorescence L1 decreases each time the fluorescence L1 passes through the first-A lens 51A and the first-B lens 51B. In the example of FIG. 2 , the cross-sectional size of the fluorescence L1 that has passed through the first-B lens 51B initially decreases as it approaches the second lens 52, then increases through a waist portion BW. The waist portion BW is the portion between the first-B lens 51B and the second lens 52 where the cross-section of the fluorescence L1 is smallest. As shown in FIG. 2 , the waist portion BW may be located so as to overlap the center of the wavelength separation filter 4 in the optical axis direction. In other words, one or more first lenses 51 may be designed so that the waist portion BW overlaps the center of the wavelength separation filter 4 in the optical axis direction.

[0035] As described above, the one or more first lenses 51 have the function of focusing the excitation light L0 from the wavelength separation filter 4 onto the wavelength conversion member 3 and the function of transmitting the fluorescence L1 from the wavelength conversion member 3 toward the effective surface of the wavelength separation filter 4.

[0036] <1-2-4. Wavelength conversion member 3> The wavelength conversion member 3 contains a fluorescent material. The wavelength conversion member 3 contains a wavelength conversion material (i.e., a fluorescent material) that converts the excitation light L0 into blue light, such as BaMgAl １０ O １７ :Eu or (Sr, Ca, Ba) １０ (P.O. ４ ) ６ Cl ２ :Eu, (Sr, Ba) １０ (P.O. ４ ) ６ Cl ２ The wavelength conversion member 3 may contain, for example, (Sr, Ba, Ca) as a wavelength conversion material that converts the excitation light L0 into blue-green light. ５ (P.O. ４ ) ３ Cl:Eu,Sr ４ Al １４ O ２５ The wavelength conversion member 3 may contain, for example, SrSi as a wavelength conversion material that converts the excitation light L0 into green light. ２ (O, Cl) ２ N ２ :Eu, (Sr, Ba, Mg) ２ SiO ４ :Eu ２＋ , or ZnS:Cu, Al, Zn ２ SiO ４ The wavelength conversion member 3 may contain, for example, Y:Mn as a wavelength conversion material that converts the excitation light L0 into red light. ２ O ２ S: Eu, Y ２ O ３ :Eu, SrCaClAlSiN ３ :Eu ２＋ , CaAlSiN ３ : Eu or CaAlSi(ON) ３The wavelength conversion member 3 may contain 3Ga as a wavelength conversion material that converts the excitation light L0 into light having a wavelength in the near-infrared region. ５ O １２ :Cr, etc. If the wavelength conversion member 3 contains multiple types of wavelength conversion materials corresponding to multiple colors of light, the wavelength conversion member 3 can emit fluorescence L1 with high color rendering. Specifically, if the excitation light L0 is light having a peak in the range of 380 nm to 415 nm and the wavelength conversion member 3 contains phosphors corresponding to red, green, and blue light, the color rendering of the fluorescence L1 can be improved.

[0037] Furthermore, the wavelength conversion member 3 may contain a resin such as a binder for binding the fine particles of the phosphor together.

[0038] The fluorescence L1 from the wavelength conversion member 3 travels toward the first lens 51 while diverging. For this reason, the size of the wavelength conversion member 3 as viewed along the optical axis AX1 may be set smaller than the size of the firstA lens 51A. Conversely, the size of the firstA lens 51A may be set larger than the size of the wavelength conversion member 3. When the wavelength conversion member 3 has a disk-like shape centered on the optical axis AX1, the diameter of the wavelength conversion member 3 may be shorter than the diameter of the firstA lens 51A. For example, the diameter of the wavelength conversion member 3 may be set to approximately 2 mm to 4 mm. When the wavelength conversion member 3 has a rectangular shape, the diagonal of the wavelength conversion member 3 may be set to approximately 2 mm to 4 mm. The diameter or diagonal of the firstA lens 51A may be set to approximately 4 mm to 15 mm, for example.

[0039] This structure allows a wider range of fluorescence L1 from the wavelength conversion member 3 to be incident on the first-A lens 51A. As shown in FIGS. 1 and 2 , the distance between the wavelength conversion member 3 and the first-A lens 51A may be narrower than the distance between the first-A lens 51A and the first-B lens 51B. The distance between the wavelength conversion member 3 and the first-A lens 51A is set to, for example, approximately 1 mm or less, and the distance between the first-A lens 51A and the first-B lens 51B is set to, for example, approximately 2 mm or more. By setting the distance between the wavelength conversion member 3 and the first-A lens 51A narrow, a larger portion of the fluorescence L1 emitted by the wavelength conversion member 3 can be incident on the first-A lens 51A.

[0040] <1-2-5. Lens optical system 5 (second lens 52)> The second lens 52 may be, for example, a convex lens. The second lens 52 is located between the wavelength separation filter 4 and the irradiation opening 6a. The second lens 52 collects the fluorescence L1 from the wavelength separation filter 4 on the irradiation opening 6a side. Note that the number of second lenses 52 located between the wavelength separation filter 4 and the irradiation opening 6a is not limited to one, and may be two or more.

[0041] The lens optical system 5 may be an imaging optical system that forms an image of the wavelength conversion member 3 on a virtual image plane IS1. That is, in the example of Figures 1 and 2, the first-A lens 51A, the first-B lens 51B, and the second lens 52 constitute the imaging optical system. The wavelength conversion member 3 has a conjugate relationship with the image plane IS1. Note that the term "conjugate relationship" here does not have a strict meaning; rather, the portion on the irradiation opening 6a side of the wavelength conversion member 3 where the fluorescence L1 is most concentrated (the portion where the magnitude of the fluorescence L1 in the cross section perpendicular to the optical axis AX1 is smallest) can be considered to be the image plane IS1.

[0042] The image plane IS1 may be located at the illumination opening 6a, for example. The image plane IS1 may be a flat surface or a curved surface. The fluorescence L1 is collected at the image plane IS1 and emitted through the illumination opening 6a into the illumination space S1. The image plane IS1 does not necessarily have to be located inside the illumination opening 6a. As shown in FIG. 2 , the image plane IS1 may be located at the boundary between the internal space of the illumination opening 6a and the internal space of the housing 6. Alternatively, the image plane IS1 may be located slightly offset from the boundary toward the internal space of the housing 6. Alternatively, the image plane IS1 may be located at the boundary between the internal space of the illumination opening 6a and the illumination space S1, or may be located slightly offset from the boundary toward the illumination space S1.

[0043] In this illumination device 1, the imaging magnification of the lens optical system 5 may be equal to or less than the ratio (=M3 / M1) of the size M3 of the irradiation opening 6a to the size M1 of the fluorescence L1 in the wavelength conversion member 3. When the fluorescence L1 is emitted from the entire surface 3b of the wavelength conversion member 3, the size M1 of the fluorescence L1 in the wavelength conversion member 3 can be said to be the size of the surface 3b of the wavelength conversion member 3 itself. The size M3 of the irradiation opening 6a is the minimum value of the opening area of ​​the irradiation opening 6a as viewed along the optical axis direction. When the irradiation opening 6a has a circular shape as viewed along the axial direction, its diameter can be set to, for example, approximately 5 mm to 15 mm. When the irradiation opening 6a has a rectangular shape as viewed along the axial direction, its diagonal can be set to, for example, approximately 5 mm to 15 mm.

[0044] The imaging magnification is the ratio of the size M2 of the fluorescence L1 on the image plane IS1 to the size M1 of the fluorescence L1 on the surface 3b of the wavelength conversion member 3.

[0045] The magnitude of the fluorescence L1 is determined by the peak value e in the light intensity distribution of the fluorescence L1 in a cross section perpendicular to the optical axis AX1. ２ Here, "e" is called the Napier's number. In other words, the outermost rays of the fluorescence L1 in FIG. 2 are defined by a contour line having a peak value e of the light intensity distribution in a cross section perpendicular to the optical axis AX1. ２The light in the area outside the area surrounded by the contour lines (i.e., both outer light rays) may be regarded as noise light.

[0046] If the imaging magnification is equal to or less than the above ratio, the size M2 of the fluorescence L1 on the image plane IS1 can be made equal to or less than the size M3 of the irradiation opening 6a, thereby reducing the possibility that the fluorescence L1 will be incident on the peripheral portion of the irradiation opening 6a in the housing 6. This reduces unnecessary reflected and scattered light leaking from the irradiation opening 6a.

[0047] Furthermore, the imaging magnification of the lens optical system 5 may be set so that the size of the fluorescence L1 passing through the irradiation opening 6a is smaller than the size of the irradiation opening 6a, thereby further reducing reflected and scattered light.

[0048] 2 and 3 , the spread angle θ2 of the fluorescence L1 in the illumination space S1 is smaller than the spread angle θ1 of the fluorescence L1 incident on the lens optical system 5. In other words, the lens optical system 5 is designed so that the spread angle θ2 is smaller than the spread angle θ1. The spread angle θ1 can also be considered to be the spread angle of the fluorescence L1 immediately before the lens optical system 5, and the spread angle θ2 can also be considered to be the spread angle of the fluorescence L1 immediately after the image plane IS1. As a specific example of the spread angle θ2, the orientation angle (e.g., half-value angle) of the fluorescence L1 in the illumination space S1 is approximately 60 degrees or less. The orientation angle of the illumination device 1 may be, for example, less than 45 degrees, less than 30 degrees, or less than 15 degrees. This can reduce the glare of the illumination devices 1 entering the field of view in an illumination space S1 in which, for example, multiple illumination devices 1 are installed at regular intervals. As a result, the comfort of the illumination space S1 can be improved.

[0049] <1-2-6. Further Details of the Various Lenses of the Lens Optical System 5> Next, examples of the firstA lens 51A and the firstB lens 51B will be described in more detail. As shown in FIGS. 1 and 2, the refractive power of the firstA lens 51A located immediately after the wavelength conversion member 3 may be greater than the refractive power of the firstB lens 51B and the refractive power of the second lens 52. This allows the degree of spread of the fluorescence L1 to be significantly reduced at the position where the firstA lens 51A is closest to the wavelength conversion member 3. In the example of FIG. 3, although the fluorescence L1 immediately after the firstA lens 51A spreads as it travels toward the firstB lens 51B, the spread angle is significantly smaller than the spread angle θ1 of the fluorescence L1 incident on the firstA lens 51A. This allows the size of the firstB lens 51B in the width direction perpendicular to the optical axis AX1 to be reduced. In other words, even if the size of the first-B lens 51B is reduced, the fluorescence L1 from the first-A lens 51A can be appropriately incident on the first-B lens 51B, which in turn allows the size of the illumination device 1 in the width direction to be reduced.

[0050] 1, the first-A lens 51A has a first surface 51Aa and a second surface 51Ab, and the first-B lens 51B has a first surface 51Ba and a second surface 51Bb. The first surface 51Aa is the surface of the first-A lens 51A that faces the wavelength conversion member 3, and the second surface 51Ab is the surface of the first-A lens 51A that faces the wavelength separation filter 4. The first surface 51Ba is the surface of the first-B lens 51B that faces the wavelength conversion member 3, and the second surface 51Bb is the surface of the first-B lens 51B that faces the wavelength separation filter 4.

[0051] As shown in FIG. 1 , the first surface 51Aa of the first-A lens 51A may be curved so as to be convex toward the wavelength conversion member 3, and the second surface 51Ab may be curved so as to be convex toward the wavelength separation filter 4. The first surface 51Aa and the second surface 51Ab of the first-A lens 51A may be curved surfaces without steps. In other words, the first-A lens 51A does not have to be a Fresnel lens. This reduces scattering or reflection in the first-A lens 51A. As a result, a comfortable illuminated space S1 with less glare can be realized. Furthermore, the curvature of the first surface 51Aa of the first-A lens 51A may be smaller than the curvature of the second surface 51Ab. In other words, the first surface 51Aa may be flatter than the second surface 51Ab. This allows the fluorescence L1 from the wavelength conversion member 3 to be incident on the first surface 51Aa of the first-A lens 51A over a wider range. In other words, it is possible to increase the proportion of the fluorescence L1 that is incident on the first surface 51Aa of the firstA lens 51A out of the total fluorescence L1 emitted by the wavelength conversion member 3, and therefore to increase the proportion of the fluorescence L1 that is emitted from the irradiation opening 6 a. Therefore, the lighting device 1 can emit the fluorescence L1 into the illumination space S1 with higher efficiency.

[0052] Conversely, the curvature of the second surface 51Ab of the first-A lens 51A may be greater than the curvature of the first surface 51Aa. If the curvature of the second surface 51Ab is greater, the refractive power of the first-A lens 51A can be improved. Therefore, the first-A lens 51A can significantly reduce the spread angle of the fluorescence L1. Therefore, the size of the illumination device 1 in the width direction can be reduced.

[0053] As shown in FIG. 1 , the first surface 51Ba of the first-B lens 51B may be curved so as to be convex toward the wavelength conversion member 3, and the second surface 51Bb may be curved so as to be convex toward the wavelength separation filter 4. The first surface 51Ba and the second surface 51Bb of the first-B lens 51B may be curved surfaces without steps. In other words, the first-B lens 51B does not have to be a Fresnel lens. This allows for the realization of a comfortable illumination space S1 with less glare. As shown in FIG. 1 , the curvature of the first surface 51Aa of the first-A lens 51A may be smaller than the curvatures of both the first surface 51Ba and the second surface 51Bb of the first-B lens 51B. Furthermore, the curvature of the second surface 51Ab of the first-A lens 51A may be larger than the curvatures of both the first surface 51Ba and the second surface 51Bb of the first-B lens 51B.

[0054] When three or more first lenses 51 are arranged, the refractive power of the first lens 51 closest to the wavelength conversion member 3 may be the greatest. This allows the first lens 51 closest to the wavelength conversion member 3 to significantly reduce the spread angle of the fluorescence L1. Therefore, the size of the illumination device 1 in the width direction can be effectively reduced.

[0055] 1, when the refractive power of the first-A lens 51A is large, for example, the curvature of the second surface 51Ab of the first-A lens 51A is very large. If the width direction size of the first-A lens 51A having the second surface 51Ab with such a large curvature is increased, it becomes difficult to manufacture the first-A lens 51A. Furthermore, the size along the optical axis AX1 of the first-A lens 51A also increases, resulting in an increase in the size of the lighting device 1.

[0056] 1, the size of the first-A lens 51A may be smaller than the size of the first-B lens 51B. In other words, the area of ​​the first-A lens 51A as viewed along the optical axis AX1 may be smaller than the area of ​​the first-B lens 51B. This makes it easier to manufacture the first-A lens 51A and also reduces the size of the lighting device 1 in the optical axis direction.

[0057] 1, the first surface 52a of the second lens 52 facing the wavelength separation filter 4 and the second surface 52b facing the irradiation opening 6a may be curved so as to be convex toward the wavelength separation filter 4 and the irradiation opening 6a, respectively. The first surface 52a and the second surface 52b of the second lens 52 may be curved surfaces without steps. In other words, the second lens 52 does not have to be a Fresnel lens. This allows for the realization of a comfortable lighting space with less glare. The curvature of the first surface 52a of the second lens 52 may be smaller than the curvature of the second surface 52b.

[0058] <1-2-7. Dependence of wavelength separation filter 4 on angle of incidence> The spectral transmittance and spectral reflectance of the dielectric multilayer film 42 are dependent on the angle of incidence. Specifically, the spectral transmittance and spectral reflectance may undergo a wavelength shift depending on the angle of incidence. In other words, as the angle of incidence deviates from a predetermined angle of incidence, the spectral transmittance in FIG. 4 may shift along the horizontal axis. In the example of FIG. 4, the transmittance Ts shifted along the horizontal axis is indicated by a two-dot chain line. Although not shown, the transmittance Tn may also shift in the same way as the transmittance Ts.

[0059] 2 , the excitation light L0 spreads as it enters the wavelength separation filter 4. Therefore, the individual rays of the excitation light L0 enter the wavelength separation filter 4 at different angles of incidence. That is, there are rays of the excitation light L0 that enter the wavelength separation filter 4 at angles of incidence other than a predetermined angle of incidence. The predetermined angle of incidence here is, for example, the angle between the optical axis AX2 of the light source 2 and the normal to the wavelength separation filter 4.

[0060] The rays of fluorescence L1 may also be incident on the wavelength separation filter 4 at different angles of incidence. That is, there are rays of fluorescence L1 that are incident on the wavelength separation filter 4 at angles of incidence other than a predetermined angle of incidence. The predetermined angle of incidence here refers to the angle between the optical axis AX1 and the normal to the wavelength separation filter 4.

[0061] As described above, the rays of the excitation light L0 may be incident on the wavelength separation filter 4 at different angles of incidence, and the rays of the fluorescence L1 may also be incident on the wavelength separation filter 4 at different angles of incidence. Therefore, both the excitation light L0 and the fluorescence L1 may be affected by the incidence angle dependency of the dielectric multilayer film 42. The greater the incidence angle dependency of the dielectric multilayer film 42, that is, the greater the shift in the spectral transmittance and spectral reflectance relative to the amount of deviation in the angle of incidence, the greater the effect on the excitation light L0 and the fluorescence L1. In other words, the greater the incidence angle dependency of the wavelength separation filter 4 on the rays of the excitation light L0 that are incident at an angle of incidence deviated from a predetermined angle of incidence, the more they are reflected by the wavelength separation filter 4 with a more shifted spectral reflectance. The fluorescence L1 that is incident at an angle of incidence deviated from the predetermined angle of incidence also passes through the wavelength separation filter 4 with a more shifted spectral transmittance.

[0062] 1 , the first surface 4 a of the dielectric multilayer film 42, which is on the side opposite to the substrate 41, is exposed inside the housing 6. In other words, the first surface 4 a of the dielectric multilayer film 42 is in contact with the air inside the housing 6. This reduces the incidence angle dependency of the dielectric multilayer film 42 compared to a structure in which the first surface 4 a of the dielectric multilayer film 42 is covered with a member having a refractive index higher than that of air. Therefore, the excitation light L0 can be reflected by the wavelength separation filter 4 with a spectral reflectance that is closer to a predetermined spectral reflectance, and the fluorescence L1 can be transmitted through the wavelength separation filter 4 with a spectral transmittance that is closer to a predetermined spectral transmittance.

[0063] Furthermore, the first lens 51 may shape the fluorescence L1 so that the multiple light rays of the fluorescence L1 are incident on the wavelength separation filter 4 with smaller incident angle variation. In other words, the refractive power of the first lens 51 may be designed so that the incident angle variation of the fluorescence L1 incident on the wavelength separation filter 4 is smaller than the incident angle variation of the fluorescence L1 incident on the firstA lens 51A. In other words, the refractive power of the first lens 51 may be designed so that the fluorescence L1 immediately after the firstB lens 51B is closer to being parallel light than the fluorescence L1 immediately before the firstA lens 51A. This makes it possible to increase the proportion of the fluorescence L1 that passes through the wavelength separation filter 4 with a spectral transmittance closer to a predetermined spectral transmittance.

[0064] Furthermore, the second lens 52 is not necessarily required. However, in a structure in which the second lens 52 is not provided, in order for the illumination device 1 to emit the fluorescence L1 at a similar divergence angle θ2, it is necessary to increase the refractive power of the first lens 51. However, if the refractive power of the first lens 51 is increased, the variation in the angle of incidence of the fluorescence L1 incident on the wavelength separation filter 4 increases.

[0065] The excitation light L0 also passes through the first lens 51. Therefore, in order to irradiate the wavelength conversion member 3 with the excitation light L0 within an appropriate range, it is necessary to increase the divergence angle of the excitation light L0 incident on the first lens 51. Consequently, the excitation light L0 needs to be incident on the wavelength separation filter 4 at a large divergence angle. In this case, the variation in the angle of incidence of each ray of the excitation light L0 on the wavelength separation filter 4 also increases. Because the spectral reflectance of the dielectric multilayer film 42 of the wavelength separation filter 4 depends on the angle of incidence, increasing the variation in the angle of incidence of the excitation light L0 on the wavelength separation filter 4 increases the proportion of the excitation light L0 that is reflected at a spectral reflectance that deviates significantly from a predetermined spectral reflectance.

[0066] In contrast, in a structure in which the second lens 52 is provided, the refractive power of the first lens 51 can be reduced, and therefore the excitation light L0 and the fluorescence L1 can be made incident on the wavelength separation filter 4 at a relatively small spread angle. This makes it possible to increase the proportion of the excitation light L0 that is reflected by the wavelength separation filter 4 at a predetermined spectral reflectance, and to increase the proportion of the fluorescence L1 that is transmitted through the wavelength separation filter 4 at a predetermined spectral transmittance.

[0067] <1-2-8. Attitude of Wavelength Separation Filter 4> Next, the angle α1 formed by the wavelength separation filter 4 and the optical axis direction will be described. The angle α1 can also be defined as an angle of 90 degrees or less between a line parallel to the first surface 4a of the dielectric multilayer film 42 and the optical axis AX1. The angle α1 may be 45 degrees or greater. More specifically, the angle α1 may be greater than 45 degrees and less than 67.5 degrees. Alternatively, the angle α1 may be greater than 45 degrees and less than 67.5 degrees. As a more specific example, the angle α1 may be approximately 50 degrees. When the angle α1 is greater than 45 degrees, the size of the wavelength separation filter 4 in the optical axis direction can be reduced. In particular, when the wavelength separation filter 4 has a plate-like shape, setting the angle α1 to greater than 45 degrees can effectively reduce the size of the wavelength separation filter 4 in the optical axis direction. Consequently, the size of the illumination device 1 in the optical axis direction can be reduced.

[0068] When the lighting device 1 is installed in the attic space, the lighting device 1 is installed with the optical axis direction aligned vertically. However, the height of the attic space may be low. Specifically, the height of the attic space may be about 10 cm.

[0069] As described above, by setting the angle α1 to be greater than 45 degrees, it is possible to reduce the size of the lighting device 1 in the optical axis direction. Therefore, the lighting device 1 can be easily installed in a low-height space above the ceiling.

[0070] Furthermore, if the distance between the first-B lens 51B and the second lens 52 becomes wider, it becomes difficult to increase the divergence angle θ2 in the optical design of the lens optical system 5. By reducing the size in the optical axis direction of the wavelength separation filter 4 located between the first-B lens 51B and the second lens 52, it is possible to further narrow the distance between the first-B lens 51B and the second lens 52. This makes it easier to design the lens optical system 5 to increase the divergence angle θ2.

[0071] Next, the angle α2 between the optical axis AX2 of the light source 2 and the optical axis AX1 will be described. The angle α2 is an angle adjacent to the angle α1. The angle α2 can also be defined as the angle between a first direction in which the wavelength conversion member 3, the wavelength separation filter 4, and the irradiation opening 6a are aligned and a second direction in which the light source 2 and the wavelength separation filter 4 are aligned. The angle α2 may be 45 degrees or greater and less than 90 degrees. Alternatively, the angle α2 may be 45 degrees or greater and 88 degrees or less. In this case, as shown in FIG. 1 , the optical axis AX2 is inclined with respect to the width direction perpendicular to the optical axis AX1. Specifically, as the optical axis AX2 approaches the light source 2 in the width direction from the wavelength separation filter 4, it is inclined so as to approach the wavelength conversion member 3 in the optical axis direction. As a more specific example, the angle α2 may be a value obtained by subtracting twice the angle α1 from 180 degrees (=180-2·α1). In this case, if angle α1 is 50 degrees, angle α2 is 80 degrees. According to this, the light ray traveling along the optical axis AX2 through the center of the excitation light L0 from the light source 2 is reflected by the wavelength separation filter 4, travels along the optical axis AX1 toward the wavelength conversion member 3, and can be incident approximately perpendicularly on the surface 3b of the wavelength conversion member 3. Therefore, the excitation light L0 can be incident on the surface 3b of the wavelength conversion member 3 evenly around the optical axis AX1.

[0072] <1-3. Housing 6> Next, a specific example of the housing 6 will be described. As shown in Fig. 1, the housing 6 may include a first housing portion 61 and a second housing portion 62. In the example of Fig. 1, the first housing portion 61 houses the wavelength conversion member 3, the wavelength separation filter 4, and the lens optical system 5, and the second housing portion 62 houses the light source 2.

[0073] <1-3-1. First Housing 61 > As shown in FIG. 1, the first housing 61 may include a main body 63 , an attachment member 64 , and a decorative frame 65 .

[0074] In the example of FIG. 1 , the main body 63 is a member that houses the wavelength separation filter 4 and the lens optical system 5. As shown in FIG. 1 , the main body 63 may include an aperture member 631 and a side wall 632. The side wall 632 has, for example, a tubular shape that surrounds the optical axis AX1. The side wall 632 may have, for example, a cylindrical shape. The side wall 632 may be a single unit, or may be a composite formed by combining multiple members. Inside the side wall 632, the first A lens 51A, the first B lens 51B, the wavelength separation filter 4, and the second lens 52 are positioned in this order in the optical axis direction.

[0075] The aperture member 631 has, for example, a plate-like shape and is positioned with its thickness direction aligned along the optical axis direction. The periphery of the aperture member 631 is connected to the edge of the side wall 632 on the wavelength conversion member 3 side. A second opening (hereinafter simply referred to as the opening) 6b penetrating the aperture member 631 in the optical axis direction is formed in the center of the aperture member 631.

[0076] The mounting member 64 may be attached to the aperture member 631 in a state in which the opening 6b of the aperture member 631 is closed. The mounting member 64 has, for example, a plate-like shape and is positioned with its thickness direction aligned with the optical axis direction. As shown in FIG. 1 , the mounting member 64 may be attached to a surface 631a of the aperture member 631 on the opposite side from the wavelength separation filter 4. The mounting member 64 may be attached to the aperture member 631 by, for example, any mounting method. As a specific example of the mounting method, the mounting member 64 may be attached to the aperture member 631 with a fixing agent such as an adhesive. Since the mounting member 64 closes the opening 6b, it can also be said to be a cover member.

[0077] The mounting member 64 has a surface 64a, a surface 64b, and a side surface 64c. The surface 64b is the surface of the mounting member 64 that faces the aperture member 631. A part of the outer periphery of the surface 64b of the mounting member 64 faces and contacts the surface 631a of the aperture member 631 in the optical axis direction. The surface 64a is the surface of the mounting member 64 on the opposite side from the surface 64b. The side surface 64c is a side surface that connects the periphery of the surface 64a of the mounting member 64 with the periphery of the surface 64b.

[0078] As shown in Fig. 1 , the wavelength conversion member 3 may be located on the surface 64b of the mounting member 64. The wavelength conversion member 3 is located on a region of the surface 64b of the mounting member 64 that faces the opening 6b of the aperture member 631 in the optical axis direction. As shown in Fig. 1 , a recess into which the wavelength conversion member 3 is filled may be formed on the surface 64b of the mounting member 64. The wavelength conversion member 3 may be bonded to the mounting member 64, for example. The mounting member 64 can function as a support that supports the wavelength conversion member 3.

[0079] The area of ​​the surface 3b of the wavelength conversion member 3 viewed along the optical axis direction may be smaller than the minimum value of the opening area of ​​the opening 6b of the aperture member 631. This allows a larger portion of the fluorescence L1 that spreads and travels from the wavelength conversion member 3 to pass through the opening 6b. Furthermore, as shown in Fig. 1 , the surface 3b of the wavelength conversion member 3 may be located flush with the surface 631a of the aperture member 631. Note that the surface 3b of the wavelength conversion member 3 may be located inside the opening 6b of the aperture member 631 or outside the opening 6b.

[0080] 1 and 3, the firstA lens 51A may be located in the opening 6b of the aperture member 631. Specifically, as shown in Fig. 3, the opening 6b of the aperture member 631 may be composed of an aperture opening 6ba and a storage opening 6bb. The storage opening 6bb is a space in which the firstA lens 51A is stored, and is located on the firstB lens 51B side of the aperture opening 6ba. The aperture opening 6ba communicates with the storage opening 6bb in the optical axis direction, and the opening area of ​​the aperture opening 6ba is smaller than the opening area of ​​the storage opening 6bb.

[0081] That is, the inner circumferential surface that forms the opening 6b of the aperture member 631 has a stepped shape. Specifically, the inner circumferential surface of the aperture member 631 has a first inner circumferential surface 633a that forms the diaphragm opening 6ba, a second inner circumferential surface 631b that forms the storage opening 6bb, and a connecting surface 633b that connects the first inner circumferential surface 633a and the second inner circumferential surface 631b. The first inner circumferential surface 633a is closer to the optical axis AX1 than the second inner circumferential surface 631b. Therefore, the opening area of ​​the diaphragm opening 6ba is smaller than the opening area of ​​the storage opening 6bb.

[0082] The aperture member 631 includes an inner peripheral protrusion 633. The inner peripheral protrusion 633 extends further toward the optical axis AX1 than the second inner peripheral surface 631b and surrounds the optical axis AX1. The inner peripheral surface of this inner peripheral protrusion 633 corresponds to the first inner peripheral surface 633a, and the surface of the inner peripheral protrusion 633 facing the firstA lens 51A corresponds to the connecting surface 633b. The second inner peripheral surface 631b of the aperture member 631 may be in contact with a side surface of the firstA lens 51A. The side surface of the firstA lens 51A is a surface that connects the periphery of the first surface 51Aa and the periphery of the second surface 51Ab. The firstA lens 51A may fit into the storage opening 6bb of the aperture member 631.

[0083] Of the fluorescence L1 from the wavelength conversion member 3, light with a divergence angle equal to or less than the predetermined divergence angle θ1 passes through the aperture 6ba and enters the lens optical system 5 (specifically, the first A lens 51A). That is, the aperture 6b (specifically, the aperture 6ba) of the aperture member 631 allows light of the fluorescence L1 with a divergence angle equal to or less than the predetermined divergence angle θ1 to pass toward the lens optical system 5. Conversely, light of the fluorescence L1 traveling at a divergence angle greater than the divergence angle θ1 (hereinafter referred to as blocked light) is blocked by the aperture member 631. In the example of FIG. 3 , the first inner peripheral surface 633a of the aperture 6ba is inclined with respect to the optical axis AX1. Specifically, the first inner peripheral surface 633a is inclined so that the opening area of ​​the aperture 6ba increases toward the wavelength conversion member 3. In other words, the first inner peripheral surface 633a of the aperture 6ba is inclined so that it moves away from the central axis of the aperture 6b (here, the optical axis AX1) toward the wavelength conversion member 3. Because the wavelength conversion member 3 is located near the diaphragm aperture 6ba, much of the shielded light from the wavelength conversion member 3 is incident on the first inner circumferential surface 633a of the diaphragm aperture 6ba. The shielded light is, for example, reflected or scattered by the first inner circumferential surface 633a of the diaphragm aperture 6ba and travels in the opposite direction from the firstA lens 51A, or part of it is absorbed by the aperture member 631.

[0084] As described above, of the fluorescence L1 output from the wavelength conversion member 3, the fluorescence L1 having a divergence angle equal to or smaller than the predetermined divergence angle θ1 passes through the diaphragm opening 6ba, and the shielded light outside of this is shielded by the opening member 631. This reduces the possibility that unnecessary reflected and scattered light will be emitted from the irradiation opening 6a. This makes it possible to realize a comfortable illumination space S1 with little glare.

[0085] The aperture member 631 may be a light-absorbing member. Light-absorbing refers to a member with an absorptivity of 60% or more in the visible light range. Furthermore, the aperture member 631 may have a first inner circumferential surface 633a formed of a light-absorbing member. The absorptivity of the first inner circumferential surface 633a for the fluorescence L1 is high. The absorptivity of the first inner circumferential surface 633a may be, for example, 60% or more, 80% or more, or 90% or more. The first inner circumferential surface 633a may have a high absorptivity for the entire wavelength range of the fluorescence L1, or may have a high absorptivity for the peak wavelength. For example, the first inner circumferential surface 633a may be formed by blackening treatment. Specific examples of blackening treatment include chemical conversion coating, plating, and painting. Matte blackening treatment or glossy blackening treatment may be used. Such a first inner circumferential surface 633a is made of a black material. The material includes, for example, at least one of a black metal, a black metal oxide film, and a black resin.

[0086] Alternatively, the first inner circumferential surface 633a may be formed of a dielectric multilayer film. The dielectric multilayer film has, for example, a structure in which a plurality of dielectric thin films are stacked. Examples of the dielectric include titanium oxide (TiO ２ ), SiO ２ , niobium pentoxide (Nb ２ O ５ ), tantalum pentoxide (Ta ２ O ５ ) and magnesium fluoride (MgF ２ Such a dielectric multilayer film may be called a low-reflection film or an anti-reflection film.

[0087] Furthermore, in the above example, the 1A lens 51A is located in the opening 6b of the aperture member 631 located immediately behind the wavelength conversion member 3. Specifically, the 1A lens 51A is located in the storage opening 6bb located immediately behind the diaphragm opening 6ba. This makes it possible to narrow the distance between the wavelength conversion member 3 and the 1A lens 51A. This allows most of the fluorescence L1 from the wavelength conversion member 3 to be incident on the 1A lens 51A.

[0088] Next, a description will be given of a mechanism for holding the wavelength separation filter 4 and the lens optical system 5. As shown in Fig. 1 , the housing 6 may further include a first inner housing 66, a second inner housing 67, a third inner housing 68, and a fourth inner housing 69, all of which are located inside the first housing portion 61.

[0089] 3 , the first inner housing 66 can function as a lens holder for holding the firstA lens 51A together with the aperture member 631. The first inner housing 66 is located between the firstA lens 51A and the firstB lens 51B. The peripheral edge of the firstA lens 51A is held in a state sandwiched between an inner peripheral protrusion 633 of the aperture member 631 and the first inner housing 66 in the optical axis direction. In other words, the inner peripheral protrusion 633 of the aperture member 631 contacts the peripheral edge of the first surface 51Aa of the firstA lens 51A, and the first inner housing 66 contacts the peripheral edge of the second surface 51Ab of the firstA lens 51A.

[0090] 3, the first inner housing 66 may include a presser member 661 and a side wall 662. The presser member 661 is located on the firstB lens 51B side of the opening member 631. The presser member 661 has a plate-like shape and is located with its thickness direction aligned with the optical axis direction. The presser member 661 faces the opening member 631 in the optical axis direction. An opening 66a is formed in the center of the presser member 661. The peripheral edge of the opening 66a in the presser member 661 contacts the second surface 51Ab of the firstA lens 51A.

[0091] 3, the fluorescence L1 spreads as it travels inside the firstA lens 51A. Therefore, as shown in Fig. 3, the opening area of ​​the opening 66a of the pressing member 661 may be larger than the opening area of ​​the diaphragm opening 6ba of the aperture member 631. This allows the fluorescence L1 to pass through the opening 66a of the pressing member more effectively, while still allowing the aperture member 631 and the pressing member 661 to properly sandwich and hold the firstA lens 51A.

[0092] 3, the inner circumferential surface of the pressing member 661 that forms the opening 66a may have a first inclined surface 661a and a second inclined surface 661b. The first inclined surface 661a is in contact with the second surface 51Ab of the firstA lens 51A and has a shape that follows the second surface 51Ab. Therefore, the first inclined surface 661a is inclined in the optical axis direction so as to move away from the optical axis AX1 as it approaches the wavelength conversion member 3. The second inclined surface 661b is located closer to the firstB lens 51B than the first inclined surface 661a. The edge of the second inclined surface 661b on the first inclined surface 661a side is connected to the edge of the first inclined surface 661a on the second inclined surface 661b side. The second inclined surface 661b is inclined in the opposite direction to the first inclined surface 661a. That is, the second inclined surface 661b is inclined so as to approach the optical axis AX1 as it approaches the first inclined surface 661a in the optical axis direction. In other words, the second inclined surface 661b is inclined so as to move away from the optical axis AX1 as it approaches the wavelength separation filter 4.

[0093] This structure allows the opening area of ​​the opening 66a to be increased while increasing the thickness of the pressing member 661. Therefore, the strength of the pressing member 661 can be improved while increasing the amount of fluorescence L1 passing through the opening 66a. Furthermore, in the above example, since the second inclined surface 661b is inclined with respect to the optical axis AX1, the fluorescence L1 transmitted through the first A lens 51A is less likely to be incident on the second inclined surface 661b. Therefore, unnecessary scattering and reflection of the fluorescence L1 can be reduced. This reduces the possibility that unnecessary reflected and scattered light will be emitted from the irradiation opening 6a.

[0094] The sidewall 662 of the first inner housing 66 has a cylindrical shape surrounding the optical axis AX1 and extends from the outer circumferential edge of the pressing member 661 toward the 1B lens 51B. The inner circumferential surface of the sidewall 662 is located closer to the optical axis AX1 than the side surface of the 1B lens 51B. The side surface of the 1B lens 51B is a surface connecting the periphery of the first surface 51Ba and the periphery of the second surface 51Bb. The outer circumferential surface of the sidewall 662 and the side surface of the 1B lens 51B may be in contact with the inner circumferential surface of the sidewall 632. The 1B lens 51B may be fitted into the inner circumferential surface of the sidewall 632. The edge of the sidewall 662 on the 1B lens 51B side may be in contact with the periphery of the first surface 51Ba of the 1B lens 51B. This allows the first inner housing 66 to function as a spacer that determines the distance between the firstA lens 51A and the firstB lens 51B.

[0095] The second inner housing 67 can function as a lens holder for holding the 1B lens 51B together with the first inner housing 66. As shown in FIG. 1 , the second inner housing 67 is located between the 1B lens 51B and the wavelength separation filter 4. The second inner housing 67 has, for example, a cylindrical shape surrounding the optical axis AX1. The inner circumferential surface of the second inner housing 67 is located closer to the optical axis AX1 than the side surface of the 1B lens 51B. The outer circumferential surface of the second inner housing 67 may be in contact with the inner circumferential surface of the side wall 632. The peripheral portion of the 1B lens 51B is held sandwiched between the first inner housing 66 and the second inner housing 67 in the optical axis direction. In other words, the edge of the first inner housing 66 on the side of the 1B lens 51B is in contact with the peripheral portion of the first surface 51Ba of the 1B lens 51B, and the edge of the second inner housing 67 on the side of the 1B lens 51B is in contact with the peripheral portion of the second surface 51Bb of the 1B lens 51B.

[0096] The edge of the second inner housing 67 on the wavelength separation filter 4 side may also be in contact with the peripheral edge of the wavelength separation filter 4. In this way, the second inner housing 67 can also function as a spacer that determines the distance between the 1B lens 51B and the wavelength separation filter 4. The end face of the second inner housing 67 that faces the wavelength separation filter 4 may have a shape that follows the first surface 4a of the wavelength separation filter 4, and may be inclined with respect to the optical axis AX1 at the same degree as the first surface 4a of the wavelength separation filter 4.

[0097] 1 , a third opening (hereinafter referred to as an introduction opening) 6c may be formed in the side wall 632 of the first housing unit 61 and the second inner housing 67. The introduction opening 6c is an opening that allows the excitation light L0 from the light source 2 located outside the first housing unit 61 to pass through and guides the excitation light L0 to the wavelength separation filter 4 inside the first housing unit 61.

[0098] The third inner housing 68, together with the second inner housing 67, can function as a filter holder 670 for holding the wavelength separation filter 4. The third inner housing 68 is located between the wavelength separation filter 4 and the second lens 52. The third inner housing 68 has, for example, a cylindrical shape surrounding the optical axis AX1. The inner circumferential surface of the third inner housing 68 is located closer to the optical axis AX1 than the periphery of the wavelength separation filter 4. The outer circumferential surface of the third inner housing 68 may be in contact with the inner circumferential surface of the side wall 632. The periphery of the wavelength separation filter 4 is held sandwiched between the second inner housing 67 and the third inner housing 68 in the optical axis direction. That is, the edge of the second inner housing 67 facing the wavelength separation filter 4 is in contact with the periphery of the first surface 4a of the wavelength separation filter 4, and the edge of the third inner housing 68 facing the wavelength separation filter 4 is in contact with the periphery of the second surface 4b, which is opposite the first surface 4a of the wavelength separation filter 4. The end face of the third inner housing 68 facing the wavelength separation filter 4 has a shape that follows the peripheral portion of the second surface 4b of the wavelength separation filter 4, and may be inclined with respect to the optical axis AX1 to the same extent as the second surface 4b of the wavelength separation filter 4.

[0099] An adhesive may be positioned between the wavelength separation filter 4 and the second inner housing 67, an adhesive may be positioned between the wavelength separation filter 4 and the third inner housing 68, or an adhesive may be positioned between the wavelength separation filter 4 and the side wall 632.

[0100] The edge of the third inner housing 68 on the second lens 52 side is in contact with the peripheral edge of the second lens 52. This allows the third inner housing 68 to also function as a spacer that determines the distance between the wavelength separation filter 4 and the second lens 52.

[0101] The fourth inner housing 69, together with the third inner housing 68, can function as a lens holder that holds the second lens 52. The fourth inner housing 69 is located between the second lens 52 and the decorative frame portion 65. The fourth inner housing 69 has, for example, a cylindrical shape that surrounds the optical axis AX1. The inner circumferential surface of the fourth inner housing 69 is located closer to the optical axis AX1 than the side surface of the second lens 52. The side surface of the second lens 52 is a surface that connects the periphery of the first surface 52a and the periphery of the second surface 52b. The outer circumferential surface of the fourth inner housing 69 and the side surface of the second lens 52 may be in contact with the inner circumferential surface of the side wall 632. The second lens 52 may be fitted into the inner circumferential surface of the side wall 632. The periphery of the second lens 52 is held sandwiched between the third inner housing 68 and the fourth inner housing 69 in the optical axis direction. That is, the edge of the third inner housing 68 on the second lens 52 side contacts the peripheral edge of the first surface 52 a of the second lens 52, and the edge of the fourth inner housing 69 on the second lens 52 side contacts the peripheral edge of the second surface 52 b of the second lens 52. The fourth inner housing 69 may be attached to the side wall 632, for example.

[0102] The decorative frame portion 65 is attached to the end of the side wall 632 opposite the opening member 631. As shown in FIG. 1 , the decorative frame portion 65 may include a plate-shaped portion 651 and a cylindrical portion 652. The plate-shaped portion 651 has a plate-like shape and is positioned such that its thickness direction is aligned with the optical axis direction. The cylindrical portion 652 has a cylindrical shape extending from the periphery of the plate-shaped portion 651 toward the wavelength conversion member 3 along the optical axis direction, and is connected to, for example, the end of the side wall 632. An irradiation opening 6a is formed in the center of the plate-shaped portion 651, penetrating the plate-shaped portion 651 in the optical axis direction. The diameter of the irradiation opening 6a is, for example, smaller than the inner diameter of the fourth inner housing 69. Note that the structure consisting of the main body portion 63 and the decorative frame portion 65 may be composed of multiple components as appropriate. For example, the structure may be divided into multiple components in the optical axis direction. The structure may be assembled by attaching these multiple components to each other.

[0103] 1, the inner circumferential surface 651a of the decorative frame portion 65 that forms the irradiation opening 6a may be inclined so that the opening area increases as the inner circumferential surface 651a approaches the illumination space S1 in the optical axis direction. In other words, the inner circumferential surface 651a may be inclined so that the inner circumferential surface 651a moves away from the central axis of the irradiation opening 6a as the inner circumferential surface 651a approaches the illumination space S1.

[0104] <1-3-2. Second Housing 62> The second housing 62 is a member that houses the light source 2. The second housing 62 is attached to the side of the first housing 61. As shown in FIG. 1, the second housing 62 may include a bottom member 621 and a side wall 622. The light source 2 is attached to the bottom member 621. The side wall 622 has a cylindrical shape that extends from the periphery of the bottom member 621 along the optical axis AX2. The edge of the side wall 622 on the opposite side to the light source 2 is connected to the side wall 632 of the first housing 61 in a state that surrounds the introduction opening 6c.

[0105] There may be no gap between the first housing part 61 and the second housing part 62. This reduces the risk of the excitation light L0 leaking outside the housing 6.

[0106] Furthermore, there may be a gap between the first housing 61 and the second housing 62. This can inhibit heat transfer between the first housing 61 and the second housing 62. This allows heat to more easily escape from the first housing 61 and the second housing 62 to the outside. As a result, heat dissipation from the lighting device 1 can be improved.

[0107] <1-3-3. Properties of Mounting Member> Next, the properties of the mounting member 64 will be described. The thermal conductivity of the mounting member 64 may be higher than the thermal conductivity of the wavelength conversion member 3. For example, a metal material with high thermal conductivity is used as the material for the mounting member 64. For example, copper (Cu), aluminum (Al), magnesium (Mg), gold (Au), silver (Ag), iron (Fe), chromium (Cr), cobalt (Co), beryllium (Be), molybdenum (Mo), tungsten (W), or an alloy is used as this metal material.

[0108] If the mounting member 64 has high thermal conductivity, it can cool the wavelength conversion member 3 from the surface 3a side. The surface 3a of the wavelength conversion member 3 is, for example, directly bonded to the surface 64b of the mounting member 64. For example, by forming phosphor pellets on the surface 64b of the mounting member 64 by hot molding or the like, the surface 3a of the wavelength conversion member 3 and the surface 64b of the mounting member 64 can be directly bonded to each other. If the mounting member 64 is directly bonded to the wavelength conversion member 3, heat from the wavelength conversion member 3 can be transferred to the mounting member 64 more quickly. Such a mounting member 64 can function as a so-called heat sink. This can reduce the degree to which the wavelength conversion member 3 is deteriorated by heat.

[0109] 1, the side surface 3c of the wavelength conversion member 3 may also be joined to the mounting member 64. This allows heat from the wavelength conversion member 3 to be transferred from the side surface 3c to the mounting member 64. Therefore, the cooling efficiency of the mounting member 64 can be improved.

[0110] The surface 64b of the mounting member 64 may be reflective to the fluorescence L1. Reflectivity here means, for example, that the reflectance is high in at least a portion of the wavelength range of the fluorescence L1. The reflectance may be, for example, 60% or more, 80% or more, or 90% or more. In this way, the fluorescence L1 generated in the wavelength conversion member 3 and heading toward the mounting member 64 is reflected by the surface 64b of the mounting member 64 and travels toward the first A lens 51A. This allows the lighting device 1 to emit a greater amount of fluorescence L1 from the irradiation opening 6a.

[0111] Furthermore, the surface 64b of the mounting member 64 may be reflective to the excitation light L0. For example, the reflectivity of the surface 64b of the mounting member 64 to the excitation light L0 may be 60% or more, 80% or more, or 90% or more. In this way, the excitation light L0 that has passed through the wavelength conversion member 3 is reflected by the surface 64b of the mounting member 64 and then enters the wavelength conversion member 3 again. This makes it possible to improve the amount of fluorescence L1 emitted by the wavelength conversion member 3. Therefore, the lighting device 1 can emit a higher amount of fluorescence L1 from the irradiation opening 6a.

[0112] Here, for example, if Al, Mg, Ag, Fe, Cr or Co is used as the metal material of the mounting member 64, the reflectance of visible light on the surface 64b of the mounting member 64 will increase, and the amount of light of the fluorescence L1 emitted in response to the excitation light L0 will increase.

[0113] The housing 6 may be made of the same material. Alternatively, at least two of the components of the housing 6 may be made of different materials. For example, the mounting member 64 may be made of a material having a higher thermal conductivity than the thermal conductivity of other components of the housing 6 (e.g., the opening member 631). For example, the mounting member 64 may be made of a metal material, and the other components of the housing 6 (e.g., the opening member 631) may be made of various synthetic resins.

[0114] <1-4. Numerical Aperture of the Lens Optical System 5> As shown in FIG. 3 , in the illumination device 1, the angle φ1 defining the numerical aperture of the lens optical system 5 may be equal to or greater than the divergence angle θ1 of the fluorescence L1 passing through the aperture 6ba. The numerical aperture is the product of the sine of half the value of the angle φ1 and the refractive index. The angle φ1 is, for example, the angle formed by both outermost rays of virtual light that can pass through the effective area of ​​the lens optical system 5. The effective area here corresponds to the area through which light can pass through which the optical performance of the lens optical system 5 can be exhibited. For example, the effective area of ​​the first lens 51 is the area of ​​the first lens 51 excluding a predetermined peripheral width. As a more specific example, the effective area of ​​the first lens 51 may be the area surrounded by the inner peripheral edge of the portion of the housing 6 that holds the periphery of the first lens 51 (here, the aperture member 631 and the first inner housing 66). In the example of FIG. 3 , the divergence angle θ1 and the angle φ1 are equal to each other.

[0115] If the spread angle θ1 is equal to or smaller than the angle φ1, the fluorescence L1 that passes through the diaphragm aperture 6ba can pass through the effective area of ​​the lens optical system 5. Therefore, almost no fluorescence L1 is incident on the edges of the first lens 51 and the second lens 52 of the lens optical system 5, and unnecessary reflection and scattering of the fluorescence L1 that occurs at these edges can be suppressed or avoided.

[0116] <1-5. Others> In the above example, the wavelength separation filter 4 is held sandwiched between the second inner housing 67 and the third inner housing 68, which are separate from each other. That is, the filter holder 670 is composed of the second inner housing 67 and the third inner housing 68, which are spaced apart in the optical axis direction. However, this is not necessarily limited to this. FIG. 5 is a diagram schematically illustrating a first example of the configuration of the filter holder 670. As shown in FIG. 5, the second inner housing 67 and the third inner housing 68 may be integrally formed by being connected in the optical axis direction. In this case, a recessed groove 67a for sandwiching the wavelength separation filter 4 in the optical axis direction is formed on the inner surface of the cylindrical filter holder 670 made up of the second inner housing 67 and the third inner housing 68. The recessed groove 67a is inclined like the wavelength separation filter 4. The peripheral edge of the wavelength separation filter 4 is inserted into the recessed groove 67a. In addition, a slit 67b connected to the recessed groove 67a is formed in the side wall of the filter holder 670. The slit 67b has an elongated shape and is inclined like the wavelength separation filter 4. The wavelength separation filter 4 is inserted into the filter holder 670 through the slit 67b. As a result, the peripheral edge of the wavelength separation filter 4 is sandwiched by the filter holder 670 in the optical axis direction.

[0117] FIG. 6 is a diagram schematically illustrating a second example of the configuration of the filter holder 670. As shown in FIG. 6, the cylindrical filter holder 670 may be divided into two separators 671 and 672 in the circumferential direction around the optical axis AX1. In this case, the slit 67b described above is unnecessary. For example, the separator 672 may be attached so that half of the periphery of the wavelength separation filter 4 is inserted into the recessed groove 67a of the separator 671, and the remaining half of the periphery of the wavelength separation filter 4 is inserted into the recessed groove 67a of the separator 672. This allows the periphery of the wavelength separation filter 4 to be sandwiched between the filter holder 670 in the optical axis direction. Note that although the filter holder 670 has a cylindrical shape in the example of FIG. 6, it may also have a rectangular cylindrical shape.

[0118] 7 is a cross-sectional view schematically illustrating an example of the configuration of an illumination device 1 according to a second embodiment. The illumination device 1 according to the second embodiment differs from the illumination device 1 according to the first embodiment in terms of the arrangement of optical elements.

[0119] In the second embodiment, the wavelength separation filter 4, the second lens 52, and the irradiation opening 6 a are arranged in this order in a linear first direction, and the wavelength conversion member 3, the first lens 51, the wavelength separation filter 4, and the light source 2 are arranged in this order in a linear second direction that intersects with the first direction. The first direction and the second direction may be perpendicular to each other.

[0120] The wavelength separation filter 4 transmits the excitation light L0 from the light source 2 toward the wavelength conversion member 3. The excitation light L0 that has transmitted through the wavelength separation filter 4 is incident on the wavelength conversion member 3 through the first lens 51. The wavelength conversion member 3 emits fluorescence L1 based on the excitation light L0. The fluorescence L1 emitted by the wavelength conversion member 3 is incident on the wavelength separation filter 4 through the first lens 51. The wavelength separation filter 4 reflects the fluorescence L1 toward the irradiation opening 6a. The fluorescence L1 reflected by the wavelength separation filter 4 is transmitted through the second lens 52 and emitted into the illumination space S1 through the irradiation opening 6a.

[0121] As described above, in the second embodiment as well, the first lens 51 is located between the wavelength separation filter 4 and the wavelength conversion member 3. Therefore, in the second embodiment as well, the lighting device 1 can emit the fluorescence L1 with high efficiency. Moreover, in the second embodiment, no optical element is located on the opposite side of the wavelength separation filter 4 from the irradiation opening 6a. This allows the size of the lighting device 1 in the first direction to be reduced. Therefore, the lighting device 1 according to the second embodiment can be installed even more easily in a low-height space above the ceiling.

[0122] 3. Third Embodiment Fig. 8 is a diagram schematically illustrating an example of the configuration of the optical system of an illumination device 1 according to a third embodiment. The illumination device 1 according to the third embodiment differs from the illumination device 1 according to the first embodiment in terms of the arrangement of optical elements. Note that in the example of Fig. 8, only the vicinity of the irradiation opening 6a of the housing 6 is shown, and other parts are not shown. Fig. 9, which will be referred to later, also shows only the vicinity of the irradiation opening 6a of the housing 6, and other parts are not shown.

[0123] 8, two second lenses 52 are shown, a second-A lens 52A and a second-B lens 52B. The second-A lens 52A and the second-B lens 52B are aligned in the optical axis direction between the wavelength separation filter 4 and the irradiation opening 6a. The second-A lens 52A and the second-B lens 52B may be, for example, convex lenses. The second-A lens 52A and the second-B lens 52B focus the fluorescence L1 on the irradiation opening 6a side.

[0124] According to the third embodiment, multiple second lenses 52 are positioned between the wavelength separation filter 4 and the irradiation opening 6a. This makes it possible to easily obtain a lens optical system 5 with a high imaging magnification while allowing the fluorescence L1 to pass through the wavelength separation filter 4 in a state closer to parallel light. In other words, the illumination device 1 can emit the fluorescence L1 at a wider divergence angle θ2.

[0125] 8 shows one first lens 51 as the first lens 51, there may be two or more first lenses 51. The number of second lenses 52 is not limited to two, and there may be three or more second lenses 52. This makes it easier to obtain the optical characteristics required for the lens optical system 5.

[0126] 9 is a diagram schematically illustrating an example of the configuration of an optical system of an illumination device 1 according to a fourth embodiment. The illumination device 1 according to the fourth embodiment differs from the illumination device 1 according to the third embodiment in that it includes a wavelength separation filter 4.

[0127] In the fourth embodiment, the wavelength separation filter 4 includes a dielectric multilayer film 42, a first prism 43, and a second prism 44. This wavelength separation filter 4 is also called a dichroic prism. The first prism 43 and the second prism 44 are transparent members containing at least one of glass such as optical glass and resin such as acrylic resin, and have, for example, an isosceles right-angled triangular prism shape.

[0128] The first prism 43 has an inclined surface 43a, a first surface 43b, a second surface 43c, and a pair of first end surfaces (not shown). The inclined surface 43a corresponds to the hypotenuse of a right-angled isosceles triangle, the first surface 43b corresponds to the first equal side of the right-angled isosceles triangle, and the second surface 43c corresponds to the second equal side of the right-angled isosceles triangle. The first surface 43b faces the first lens 51 in the optical axis direction, and the second surface 43c faces the light source 2 in the direction along the optical axis AX2. The pair of first end surfaces are surfaces located at both ends in the directions perpendicular to both the optical axes AX1 and AX2.

[0129] The second prism 44 has an inclined surface 44a, a first surface 44b, a second surface 44c, and a pair of second end surfaces (not shown). The inclined surface 44a corresponds to the hypotenuse of a right-angled isosceles triangle, the first surface 44b corresponds to the first equal side of the right-angled isosceles triangle, and the second surface 44c corresponds to the second equal side of the right-angled isosceles triangle. The first surface 44b faces the second lens 52 in the optical axis direction. The pair of second end surfaces are surfaces located at both ends in a direction perpendicular to both the optical axis AX1 and the optical axis AX2.

[0130] The first prism 43 and the second prism 44 are positioned such that the inclined surface 43 a and the inclined surface 44 a face each other. The dielectric multilayer film 42 is positioned between the inclined surface 43 a of the first prism 43 and the inclined surface 44 a of the second prism 44. The wavelength separation filter 4 has an overall cubic shape.

[0131] The excitation light L0 from the light source 2 is incident on the second surface 43c of the first prism 43. The second surface 43c of the first prism 43 is, for example, perpendicular to the optical axis AX2 of the light source 2. The excitation light L0 travels from the second surface 43c inside the first prism 43 toward the dielectric multilayer film 42 and is reflected by the dielectric multilayer film 42. The excitation light L0 reflected by the dielectric multilayer film 42 travels inside the first prism 43 toward the first surface 43b and passes through the first surface 43b. The first surface 43b of the first prism 43 is, for example, perpendicular to the optical axis AX1. The excitation light L0 is incident on the wavelength conversion member 3 from the first surface 43b through the first lens 51. The wavelength conversion member 3 emits fluorescence L1 based on the excitation light L0.

[0132] Fluorescence L1 emitted by the wavelength conversion member 3 is incident on the first surface 43b of the first prism 43 through the first lens 51. The fluorescence L1 travels from the first surface 43b inside the first prism 43 toward the dielectric multilayer film 42 and is transmitted through the dielectric multilayer film 42. The fluorescence L1 that has transmitted through the dielectric multilayer film 42 travels inside the second prism 44 toward the first surface 44b and passes through the first surface 44b. The first surface 44b of the second prism 44 is, for example, approximately parallel to the first surface 43b of the first prism 43 and perpendicular to the optical axis AX1. The fluorescence L1 travels from the first surface 44b of the second prism 44 to the second lens 52 and is emitted through the second lens 52 from the irradiation opening 6a into the illumination space S1.

[0133] As described above, in the fourth embodiment, the fluorescence L1 enters the wavelength separation filter 4 at the first surface 43b of the first prism 43, which is perpendicular to the optical axis direction, and exits from the first surface 44b of the second prism 44, which is parallel to the first surface 43b. This reduces the deviation of the optical path of the fluorescence L1 in the width direction, which is perpendicular to the optical axis direction, that occurs when the fluorescence L1 passes through the wavelength separation filter 4. In other words, it reduces the amount of misalignment between the optical axis AX1 of the first lens 51, which is located between the wavelength separation filter 4 and the wavelength conversion member 3, and the optical axis of the second lens 52, which is located between the wavelength separation filter 4 and the irradiation opening 6a. This allows the first lens 51 and the second lens 52 to be held approximately coaxially, simplifying the design of the housing 6.

[0134] Although the wavelength separation filter 4 has a cubic shape in the above example, it may have a cylindrical shape with the optical axis direction as the height direction, for example.

[0135] Although the lighting device 1 has been described in detail above, the above description is merely an example in all respects, and the lighting device 1 is not limited thereto. It is understood that countless variations not illustrated can be envisioned without departing from the scope of this disclosure. The configurations described in the above embodiments and variations can be combined or omitted as appropriate, as long as they are not mutually inconsistent.

[0136] It goes without saying that all or part of the components constituting each of the above-described embodiments and various modified examples can be combined as appropriate within the scope of not causing any contradiction.

[0137] For example, the first lens 51 and the second lens 52 are not necessarily limited to convex lenses. Concave lenses, meniscus lenses, and convex lenses may be used as appropriate. Furthermore, the first lens 51 may be a spherical lens or an aspherical lens. The second lens 52 may also be a spherical lens or an aspherical lens.

[0138] This disclosure includes the following:

[0139] In one embodiment, (1) an illumination device includes: a housing having a first opening; a light source that emits excitation light; a wavelength conversion member located inside the housing, into which the excitation light from the light source is incident and which emits fluorescence based on the excitation light and having a spectrum different from that of the excitation light; a wavelength separation filter located inside the housing, which guides the excitation light from the light source to the wavelength conversion member and guides the fluorescence from the wavelength conversion member to the first opening; and a lens optical system located inside the housing between the wavelength separation filter and the wavelength conversion member, which includes one or more first lenses that focus the excitation light on the wavelength conversion member and transmit the fluorescence from the wavelength conversion member toward an effective surface of the wavelength separation filter.

[0140] (2) In the illumination device of (1) above, the lens optical system can image the fluorescence from the wavelength conversion member on the first opening side and emit the fluorescence from the first opening, and the imaging magnification of the lens optical system may be equal to or less than the ratio of the size of the first opening to the size of the fluorescence in the wavelength conversion member.

[0141] (3) In the lighting device of (1) or (2) above, the first lens may include a first A lens located between the wavelength conversion member and the wavelength separation filter, and a first B lens located between the wavelength conversion member and the wavelength separation filter and closer to the wavelength separation filter than the first A lens.

[0142] (4) In the lighting device of (3) above, the refractive power of the first A lens may be greater than the refractive power of the first B lens.

[0143] (5) In the lighting device of (3) or (4) above, the first lens B may be larger in size than the first lens A.

[0144] (6) In any one of the illumination devices (1) to (5) above, the first lens may have a first surface on the wavelength conversion member side and a second surface on the wavelength separation filter side, and the curvature of the first surface may be smaller than the curvature of the second surface.

[0145] (7) In the illumination device according to any one of (1) to (6) above, the lens optical system may further include a second lens positioned between the wavelength separation filter and the first opening.

[0146] (8) In the illumination device according to any one of (1) to (7) above, a spread angle of the fluorescence emitted from the first opening may be smaller than a spread angle of the fluorescence incident on the lens optical system.

[0147] (9) In any one of the lighting devices (1) to (8) above, the wavelength conversion member, the wavelength separation filter, and the first opening can be aligned in a predetermined first direction, the light source and the wavelength separation filter can be aligned in a second direction intersecting the first direction, and the wavelength separation filter can reflect the excitation light from the light source toward the wavelength conversion member and transmit the fluorescence from the wavelength conversion member toward the first opening.

[0148] (10) In the lighting device of (9) above, the first lens and the second lens can be aligned in the first direction.

[0149] (11) In any one of the lighting devices (1) to (9) above, the wavelength separation filter and the first opening can be aligned in a predetermined first direction, the light source, the wavelength separation filter, and the wavelength conversion member can be aligned in a second direction intersecting the first direction, and the wavelength separation filter can transmit the excitation light from the light source to the wavelength conversion member side and reflect the fluorescence from the wavelength conversion member to the first opening side.

[0150] (12) In the illumination device of (10) or (11) above, the angle formed between the dielectric multilayer film of the wavelength separation filter and the first direction may be 45 degrees or more.

[0151] (13) In the lighting device according to any one of (1) to (12) above, the housing may include a filter holder that holds the peripheral portion of the wavelength separation filter in a direction along the optical axis of the first lens.

[0152] (14) Any one of the illumination devices (1) to (13) above may further include an aperture member having a second opening that allows the fluorescence from the wavelength conversion member, the fluorescence having a predetermined divergence angle or less, to pass toward the lens optical system and blocks the fluorescence having a divergence angle larger than the predetermined divergence angle.

[0153] (15) In the illumination device of (14) above, the angle defining the numerical aperture of the lens optical system may be equal to or greater than the predetermined divergence angle.

[0154] (16) In the lighting device of (14) or (15) above, the inner circumferential surface forming the second opening of the opening member may have a portion that is inclined so that the opening area increases as it approaches the wavelength conversion member.

[0155] (17) In the lighting device according to any one of (14) to (16) above, the first lens may be positioned at the second opening.

[0156] (18) In the lighting device of (17) above, the housing may further include an inner housing that sandwiches the peripheral portion of the first lens together with the aperture member, the first lens may have a first surface on the wavelength conversion member side and a second surface on the wavelength separation filter side, the aperture member may be in contact with the peripheral portion of the first surface of the first lens, the inner housing may include a pressing member, the pressing member may have a first inclined surface in contact with the peripheral portion of the second surface of the first lens and a second inclined surface located closer to the wavelength separation filter than the first inclined surface, and the second inclined surface may be inclined so as to move away from the optical axis of the first lens as it approaches the wavelength separation filter.

[0157] (19) In any one of the lighting devices (14) to (18) above, the housing may include a mounting member attached to a surface of the opening member on the opposite side from the wavelength separation filter in a state where the second opening is blocked, and the wavelength conversion member may be located in a region of the mounting member facing the second opening.

[0158] (20) In the lighting device of (19) above, the thermal conductivity of the mounting member may be higher than the thermal conductivity of the wavelength conversion member.

[0159] (21) In any one of the lighting devices (1) to (20) above, the housing may include a first housing portion that houses the wavelength separation filter and the lens optical system, and a second housing portion that houses the light source, and the first housing portion may have a third opening that allows the excitation light from the light source to pass toward the wavelength separation filter.

[0160] REFERENCE SIGNS LIST 1 Illumination device 2 Light source 3 Wavelength conversion member 4 Wavelength separation filter 5 Lens optical system 51 First lens 51A First lens (1A lens) 51Aa First surface 51Ab Second surface 51B First lens (1B lens) 52 Second lens 52A Second lens (2A lens) 52B Second lens (2B lens) 6 Housing 61 First housing part 62 Second housing part 631 Opening member 66 Inner housing (first inner housing) 661 Pressing member 670 Filter holder 6a First opening (irradiation opening) 6b Second opening (opening) 6c Third opening (inlet opening) L0 Excitation light L1 Fluorescence

Claims

1. a housing having a first opening; A light source that emits excitation light; a wavelength conversion member located inside the housing, receiving the excitation light from the light source and emitting fluorescence having a spectrum different from that of the excitation light based on the excitation light; a wavelength separation filter located inside the housing, for guiding the excitation light from the light source to the wavelength conversion member and guiding the fluorescence from the wavelength conversion member to the first opening; a lens optical system including one or more first lenses located inside the housing between the wavelength separation filter and the wavelength conversion member, the lens optical system focusing the excitation light on the wavelength conversion member and transmitting the fluorescence from the wavelength conversion member toward an effective surface of the wavelength separation filter; A lighting device comprising:

2. 2. The lighting device according to claim 1, the lens optical system forms an image of the fluorescence from the wavelength conversion member on the first opening side and causes the fluorescence to exit from the first opening; an imaging magnification of the lens optical system is equal to or smaller than a ratio of a size of the first opening to a size of the fluorescence in the wavelength conversion member.

3. 3. The lighting device according to claim 1, The first lens is a first A lens located between the wavelength conversion member and the wavelength separation filter; a first lens B located between the wavelength conversion member and the wavelength separation filter and closer to the wavelength separation filter than the first lens A; 13. A lighting device comprising:

4. 4. The lighting device according to claim 3, An illumination device, wherein the refractive power of the first A lens is greater than the refractive power of the first B lens.

5. 4. The lighting device according to claim 3, An illumination device, wherein the size of the first B lens is larger than the size of the first A lens.

6. 3. The lighting device according to claim 1, the first lens has a first surface on the wavelength conversion member side and a second surface on the wavelength separation filter side, A lighting device, wherein the curvature of the first surface is smaller than the curvature of the second surface.

7. 3. The lighting device according to claim 1, The lens optical system further includes a second lens positioned between the wavelength separation filter and the first opening.

8. 3. The lighting device according to claim 1, a spread angle of the fluorescent light emitted from the first opening is smaller than a spread angle of the fluorescent light incident on the lens optical system.

9. 3. The lighting device according to claim 1, the wavelength conversion member, the wavelength separation filter, and the first opening are aligned in a predetermined first direction, the light source and the wavelength separation filter are aligned in a second direction intersecting the first direction, The wavelength separation filter reflects the excitation light from the light source toward the wavelength conversion member and transmits the fluorescence from the wavelength conversion member toward the first opening.

10. 10. The lighting device according to claim 9, An illumination device, wherein the first lens and the second lens are aligned in the first direction.

11. 3. The lighting device according to claim 1, the wavelength separation filter and the first opening are aligned in a predetermined first direction, the light source, the wavelength separation filter, and the wavelength conversion member are aligned in a second direction intersecting the first direction, The wavelength separation filter transmits the excitation light from the light source toward the wavelength conversion member and reflects the fluorescence from the wavelength conversion member toward the first opening.

12. 11. The lighting device according to claim 10, an angle between the dielectric multilayer film of the wavelength separation filter and the first direction is equal to or greater than 45 degrees.

13. 3. The lighting device according to claim 1, The housing includes: an illumination device including a filter holder that holds a peripheral portion of the wavelength separation filter in a direction along the optical axis of the first lens;

14. 3. The lighting device according to claim 1, the illumination device further comprising an aperture member having a second opening that allows the fluorescence from the wavelength conversion member to pass toward the lens optical system, the fluorescence having a predetermined spread angle or less, and blocks the fluorescence having a spread angle larger than the predetermined spread angle.

15. 15. The lighting device according to claim 14, An illumination device, wherein an angle defining a numerical aperture of the lens optical system is equal to or greater than the predetermined spread angle.

16. 15. The lighting device according to claim 14, an inner circumferential surface that forms the second opening of the opening member has a portion that is inclined so that an opening area increases toward the wavelength conversion member.

17. 15. The lighting device according to claim 14, The first lens is located at the second opening.

18. 18. The lighting device according to claim 17, the housing further includes an inner housing that sandwiches a peripheral portion of the first lens together with the opening member, the first lens has a first surface on the wavelength conversion member side and a second surface on the wavelength separation filter side, the aperture member is in contact with a peripheral portion of the first surface of the first lens, The inner housing includes a pressing member, the pressing member has a first inclined surface in contact with a peripheral portion of the second surface of the first lens, and a second inclined surface located closer to the wavelength separation filter than the first inclined surface, The second inclined surface is inclined so as to move away from the optical axis of the first lens as it approaches the wavelength separation filter.

19. 15. The lighting device according to claim 14, the housing includes an attachment member attached to a surface of the opening member on a side opposite to the wavelength separation filter in a state in which the second opening is closed, The wavelength conversion member is located in a region of the mounting member facing the second opening.

20. 20. The lighting device according to claim 19, A lighting device, wherein the mounting member has a higher thermal conductivity than the wavelength conversion member.

21. 3. The lighting device according to claim 1, The housing includes: a first housing portion that houses the wavelength separation filter and the lens optical system; A second housing portion that houses the light source; Including, The first housing portion has a third opening through which the excitation light from the light source passes toward the wavelength separation filter.