Light-emitting device

Abstract

To provide a light-emitting device capable of reducing an irregular color of a mixed light, obtained by mixing a light ejected from a semiconductor light-emitting element and a fluorescence emitted from a fluorescence substance.SOLUTION: A light-emitting device comprises: a plurality of semiconductor light-emitting elements; an optical element that outputs a plurality of collimated beams by collimating a light ejected from each of the plurality of semiconductor light-emitting elements; a light collector part that includes a nonspherical for focusing the plurality of collimated beams; and a wavelength conversion part that is a wavelength conversion part including a translucent region that contains a light incident surface into which the plurality of collimated beams is entered and a reflection region surrounding the translucent region, in which the translucent region contains a fluorescence substance executed by the plurality of collimated beams focused by the light collector part.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] The present disclosure relates to a light emitting device. [Background technology]

[0002] Many light emitting devices have been proposed that emit mixed light obtained by mixing light emitted from a semiconductor light emitting element and fluorescence emitted from a phosphor. In such light emitting devices, for example, blue light emitted from the semiconductor light emitting element excites a phosphor that emits yellow fluorescence, and the blue light passing through the phosphor-containing portion is mixed with the yellow fluorescence emitted from the phosphor to obtain white mixed light (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2012 / 124302 Summary of the Invention [Problem to be solved by the invention]

[0004] When a phosphor is irradiated with light emitted from a semiconductor light-emitting element, the mixed light obtained by mixing the light from the semiconductor light-emitting element that passes through the phosphor-containing portion with the fluorescence emitted from the phosphor may have color unevenness. [Means for solving the problem]

[0005] In one embodiment, the light emitting device of the present disclosure comprises a plurality of semiconductor light emitting elements, an optical element that collimates light emitted from each of the plurality of semiconductor light emitting elements to output a plurality of collimated beams, a focusing section having an aspherical surface that converges the plurality of collimated beams, and a wavelength converting section having a light-transmitting region including a light incident surface on which the plurality of collimated beams are incident and a reflective region surrounding the light-transmitting region, wherein the light-transmitting region contains a phosphor that is excited by the plurality of collimated beams converged by the focusing section. [Effects of the Invention]

[0006] According to the light emitting device described above in the present disclosure, it is possible to provide a light emitting device that suppresses color unevenness in mixed light obtained by mixing light emitted from a semiconductor light emitting element and fluorescent light emitted from a phosphor. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1A is a perspective view schematically showing a wavelength converting section 40 having a light-transmitting region 40t containing a phosphor and a reflective region 40r surrounding the light-transmitting region 40t. [Figure 1B] FIG. 1B is a diagram showing the calculation results of the intensity distribution of a 2-row, 5-column collimated beam converged by a spherical lens on a light incident surface 40s1 of a light-transmitting region 40t. [Figure 1C] FIG. 1C is a diagram schematically showing the color distribution of the mixed light emitted from the light exit surface 40s2 of the light-transmitting region 40t. [Figure 2A] FIG. 2A is a perspective view schematically illustrating a light emitting device 100 according to an embodiment of the present disclosure. [Figure 2B] FIG. 2B is a perspective view schematically showing the inside of the light emitting device 100 shown in FIG. 2A. [Figure 3A] FIG. 3A is a side view seen from the X direction, schematically illustrating how the collimated beam 20b emitted from the light source 20 is converged by the aspherical lens 30 and enters the light incident surface 40s1 of the light-transmitting region 40t in the wavelength converting section 40. [Figure 3B]3B is a side view seen from the Y direction, schematically showing how the collimated beam 20b emitted from the light source 20 is converged by the aspherical lens 30 and enters the light incident surface 40s1 of the light-transmitting region 40t in the wavelength conversion section 40. [Figure 4] FIG. 4 is a graph plotting the curved surface of the lens shown in equation (1). [Figure 5] FIG. 5 is a diagram showing the calculation results of the intensity distribution of a 2-row, 5-column collimated illumination beam converged by an aspherical lens 30 with a conic constant k=+0.5. [Figure 6] FIG. 6 shows the calculated intensity distribution of a 2-by-5 ​​collimated illumination beam focused by lenses with various conic constants. [Figure 7A] FIG. 7A is a diagram of the light source 20 shown in FIG. 2B, in which the frame 22 and the cover 23 are omitted. [Figure 7B] 7B is a cross-sectional view in the YZ plane that schematically shows how the laser light emitted from the semiconductor light emitting element 25 is reflected by the reflecting surface 27r of the light reflecting member 27 and collimated by the collimating lens 24l of the optical element 24. FIG. [Figure 7C] FIG. 7C is a cross-sectional view in the XZ plane that schematically shows how the laser light emitted from the semiconductor light emitting element 25 is reflected by the reflecting surface 27r of the light reflecting member 27 and collimated by the collimating lens 24l of the optical element 24. [Figure 8A] Figure 8A is a side view viewed from the Y direction, schematically showing how the collimated beam 20b emitted from the light source 20 is converged by the parabolic reflector 31 in the modified example and enters the light incident surface 40s1 of the light-transmitting region 40t in the wavelength conversion section 40. [Figure 8B] Figure 8B is a side view viewed from the Y direction, schematically showing how the collimated beam 20b emitted from the light source 20 is converged by the parabolic reflector 31 in the modified example and enters the light incident surface 40s1 of the light-transmitting region 40t in the wavelength conversion section 40. [Figure 9]FIG. 9 is a diagram schematically showing the spectrum of excitation light of a single wavelength and the spectrum of fluorescence. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Fluorescence spectrum) Before describing the embodiments of the present disclosure, the spectrum of fluorescence emitted from a phosphor when the phosphor is excited by light (excitation light) with a narrow spectral width such as laser light will be described.

[0009] FIG. 9 is a diagram showing a schematic diagram of the spectrum of excitation light and the spectrum of fluorescence. As shown in FIG. 9, the spectral width of excitation light is narrow, whereas the spectral width of fluorescence is wide. The spectrum of fluorescence is in a wavelength range longer than the wavelength of the excitation light. In reality, when a phosphor is irradiated with excitation light, part of the excitation light excites the phosphor, and the remaining part is extracted from the phosphor-containing portion without being wavelength-converted by passing through the phosphor or being reflected by the phosphor. Therefore, light is obtained that is a mixture of the excitation light that passes through the phosphor and the fluorescence emitted from the phosphor. For example, when a blue laser beam with a wavelength of 455 nm is used to excite YAG (Yttrium Aluminum When a garnet phosphor is excited, the phosphor emits yellow fluorescence. White light is obtained by mixing the blue laser light that passes through the phosphor with the yellow fluorescence emitted from the phosphor. This white mixed light can be used, for example, in lighting fixtures. Note that the color of the mixed light is typically white, but is not limited to this, and the color of the mixed light can be adjusted by the combination of excitation light and phosphor.

[0010] (Findings underlying the embodiments of the present disclosure) Next, the findings that form the basis of the embodiments of the present disclosure will be described with reference to Figures 1A to 1C. When irradiating a phosphor with excitation light to obtain mixed light of the excitation light that passes through the phosphor and the fluorescence emitted from the phosphor, the phosphor can be used in the following manner.

[0011] FIG. 1A is a perspective view schematically illustrating a wavelength conversion unit 40 having a light-transmitting region 40t containing a phosphor and a surrounding reflective region 40r. The light-transmitting region 40t includes an exposed, parallel light incident surface 40s1 and a light exit surface 40s2. The light-transmitting region 40t may be, for example, a ceramic containing a phosphor, i.e., a phosphor ceramic. Because the fluorescence emitted by the phosphor is substantially undistributed, in the phosphor ceramic, a portion of the fluorescence is directed toward the reflective region 40r and reflected by the reflective region 40r. The phosphor ceramic may be formed, for example, from an inorganic binder and a phosphor. The reflective region 40r may be formed, for example, from ceramic. In the example shown in FIG. 1A, the light-transmitting region 40t is primarily formed from a YAG phosphor and an aluminum oxide binder, while the reflective region 40r is primarily formed from aluminum oxide. The light-transmitting region 40t and the reflective region 40r, both of which contain aluminum oxide, have high adhesion.

[0012] For example, a semiconductor laser package emitting multiple blue collimated beams can be used as an excitation light source for exciting the YAG phosphor contained in the light-transmitting region 40t. By converging the multiple collimated beams using a single focusing lens and irradiating the light incident surface 40s1 of the light-transmitting region 40t with the converged multiple beams, mixed light can be obtained. A collimated beam refers to a beam that has been collimated so that its beam diameter is constant in the direction of beam propagation. However, the beam diameter may not be strictly constant. Furthermore, when a collimated beam is converged using a focusing lens, the beam diameter gradually narrows, reaches a minimum at the beam waist, and then gradually expands. For simplicity's sake, the term "collimated beam" in this specification also includes the collimated beam after passing through the focusing lens.

[0013] FIG. 1B shows the calculated intensity distribution of a 2-row, 5-column collimated beam converged by a spherical lens on the light incident surface 40s1 of the light-transmitting region 40t. In FIG. 1B, the light intensity is shown relatively, with white representing 0% and black representing 100%. Hereinafter, the intensity distribution of the collimated beam irradiated onto the light-transmitting region 40t on the light incident surface 40s1 will be referred to simply as the "intensity distribution of the collimated beam." Details of the calculation conditions will be described later. The area enclosed by a black rectangular frame represents the light incident surface 40s1 of the light-transmitting region 40t. The light incident surface 40s1 of the light-transmitting region 40t is located away from the focal point of the collimated beam converged by the spherical lens. As shown in FIG. 1B, the central portion of the light incident surface 40s1 of the light-transmitting region 40t is primarily illuminated. Although the multiple collimated beams diverge as they move away from the center, in the example shown in FIG. 1B, the degree of divergence is not so great that the edges of the light incident surface 40s1, particularly the four corners, are barely illuminated. The phosphors excited by the collimated beams incident on the light-transmitting region 40t emit fluorescence. Therefore, white light, a mixture of the blue light passing through the light-transmitting region 40t and the yellow fluorescence emitted from the YAG phosphor, should be emitted from the light-exiting surface 40s2 of the light-transmitting region 40t. However, in reality, this mixed light may have color variations.

[0014] FIG. 1C is a diagram showing a schematic diagram of the color distribution of the mixed light emitted from the light exit surface 40s2 of the light-transmitting region 40t. The white region represents the region where white light is emitted, and the shaded region represents the region where light with a stronger yellow tint is emitted. It can be seen that a large amount of white light is emitted from the center of the light exit surface 40s2 of the light-transmitting region 40t, but light with a stronger yellow tint is emitted from the edge portions, particularly the four corners, resulting in significant color unevenness. The following is thought to be the reason for this. A portion of the fluorescence emitted from the locations irradiated with the four collimated beams at the edges in the row direction (X direction) travels toward the reflective region 40r, is reflected by the reflective region 40r, and then is emitted from the light exit surface 40s2. At the corners of the reflective region 40r, the fluorescence is reflected by two mutually perpendicular surfaces. As a result, the proportion of yellow light becomes greater than the proportion of blue light, and the mixed light becomes yellow at the edge portions, particularly at the four corners, of the light exit surface 40s2 of the light-transmitting region 40t.

[0015] The inventors of the present invention have considered that color unevenness is caused by the intensity distribution of the collimated irradiated beam at the light incident surface of the light-transmitting region, and have conceived a novel light-emitting device that can reduce color unevenness. This light-emitting device includes a focusing unit having an aspherical surface that converges multiple collimated beams emitted from a light source. The shape of this aspherical surface is appropriately designed so that the intensity distribution of the converged collimated irradiated beam reduces color unevenness in the mixed light. Details of the focusing unit will be described later.

[0016] (Embodiment) An embodiment of the present disclosure will be described below with reference to the drawings. However, the embodiment described below embodies the technical concept of the present invention and does not limit the present invention. Furthermore, in the following description, the same names and symbols indicate the same or similar components, and detailed description will be omitted as appropriate. Note that the size and positional relationship of components shown in each drawing may be exaggerated for clarity of explanation.

[0017] In this specification, "placing a component on a surface" refers to either a state in which a component is placed directly on a surface, or a state in which a component is placed directly on another object that is placed directly on that surface. In other words, a state in which a component is placed above a surface and is physically connected to the surface with or without an intermediary is expressed as a state in which a component is placed on that surface. Note that when specifying that a component is placed directly on a surface, the term "directly" is used. When it is not specified that a component is placed directly, it means that either is acceptable.

[0018] <Configuration example of light-emitting device> First, a configuration example of a light emitting device according to an embodiment of the present disclosure will be described with reference to FIGS. 2A to 2D.

[0019] Fig. 2A is a perspective view schematically illustrating a light emitting device 100 according to an embodiment of the present disclosure. Fig. 2B is a perspective view schematically illustrating the interior of the light emitting device 100 shown in Fig. 2A. In Fig. 2B, the outline of the housing 50 is indicated by a dashed line. For reference, the drawing shows an X direction, a Y direction, and a Z direction, which are orthogonal to each other.

[0020] The light-emitting device 100 of this embodiment includes a substrate 10 having a principal surface 10s, a light source 20 located on the principal surface 10s and emitting collimated beams arranged in two rows and five columns, an aspherical lens 30 having a convex portion 30c that converges the collimated beam, a wavelength conversion unit 40 having a light-transmitting region 40t on the optical axis of the aspherical lens 30, and a housing 50 that houses the light source 20 and the aspherical lens 30. The row direction is parallel to the X direction, and the column direction is parallel to the Y direction. In this specification, "upward" refers to the direction in which the light source 20 is disposed relative to the principal surface 10s of the substrate 10. The light-emitting device 100 may be oriented in any direction during use.

[0021] The substrate 10 in this embodiment has, for example, a main surface 10s parallel to the XY plane and a thickness in the Z direction. The substrate 10 is desirably formed from a material with relatively high thermal conductivity so as to quickly dissipate heat generated from the light source 20 to the outside. The thermal conductivity of the substrate 10 is, for example, 20 W / mK or higher. Examples of the main material of the substrate 10 include metals such as Cu, Al, Fe, Ni, and Mo, and ceramics such as aluminum nitride and silicon carbide.

[0022] The light source 20 in this embodiment includes a base 21, semiconductor light-emitting elements arranged in two rows and five columns on the main surface of the base 21, a frame 22 with lead terminals 22l provided on the main surface of the base 21 and surrounding the semiconductor light-emitting elements, a lid 23 provided on the frame of the frame 22, and an optical element 24 provided on the lid 23. The optical element 24 collimates the light emitted from the semiconductor light-emitting elements arranged in two rows and five columns within the light source 20 and outputs two rows and five columns of collimated beams in a direction parallel to the optical axis of the aspherical lens 30 (Z direction). The propagation directions of these collimated beams are parallel to each other. However, the propagation directions do not need to be strictly parallel. In this specification, "parallel" is not limited to mathematically strict "parallel." In this specification, "parallel" can tolerate a deviation of 1.5 degrees or less from strict parallelism. If there are multiple collimated beams, the light-transmitting region 40t containing a phosphor can be irradiated with multiple collimated beams. When the light-transmitting region 40t in the wavelength conversion unit 40 contains a YAG phosphor, the wavelength of the blue collimated beam is, for example, 420 nm or more and 480 nm or less. An appropriate wavelength of the collimated beam is selected depending on the type of phosphor. The size of the light source 20 in the X and Y directions is, for example, 25 mm or more and 35 mm or less, and the thickness in the Z direction is, for example, 10 mm or more and 15 mm or less. Details of the light source 20 will be described later.

[0023] The aspherical lens 30 in this embodiment is, for example, a plano-convex lens having a convex portion 30c and a flat portion 30f. The refractive index of the convex portion 30c and the flat portion 30f is, for example, 1.4 or more and 2.1 or less. The convex portion 30c is provided on the side on which the collimated beam is incident, but may be provided on the side opposite to the side on which the collimated beam is incident. The flat portion 30f is not necessarily provided. In the example shown in FIG. 2B, the convex portion 30c is thicker than the flat portion 30f, but the flat portion 30f may also be thicker than the convex portion 30c. The light-collecting portion having an aspherical surface in the present disclosure may be, for example, an aspherical lens 30.

[0024] The convex portion 30c and / or the flat portion 30f of the aspherical lens 30 may be formed from at least one of glass, quartz, and sapphire, for example. The size of the aspherical lens 30 in the X and Y directions is, for example, 2 mm or more and 200 mm or less, and the thickness in the Z direction is, for example, 2 mm or more and 150 mm or less. The top view shape of the aspherical lens 30, i.e., the shape when viewed from the Z direction, is, for example, circular. The gap in the Z direction between the light source 20 and the aspherical lens 30 is, for example, 1 mm or more and 300 mm or less. Details of the aspherical shape of the surface of the convex portion 30c of the aspherical lens 30 will be described later.

[0025] The wavelength converting section 40 in this embodiment is as described with reference to Fig. 1A. The light incident surface 40s1 of the light-transmitting region 40t has a rectangular shape, but may have a polygonal, circular, elliptical, or similar shape.

[0026] The light-transmitting region 40t in the wavelength conversion unit 40 includes a YAG phosphor that emits yellow fluorescence when excited by blue light, but is not limited to this. For example, the light-transmitting region 40t may include a first phosphor that emits yellow or green fluorescence when excited by blue light and a second phosphor that emits red fluorescence. By irradiating the light incident surface 40s1 of such a light-transmitting region 40t with blue light, a white mixed light can be obtained from the light exit surface 40s2 of the light-transmitting region 40t.

[0027] The reflective region 40r in the wavelength conversion unit 40 may be formed primarily from aluminum oxide, zirconium oxide, or titanium oxide. The reflective region 40r may contain additives such as yttrium oxide, zirconium oxide, lutetium oxide, or lanthanum oxide to reduce light transmittance. When the reflective region 40r is made of ceramics, the higher the porosity of the reflective region 40r, the higher the light reflectance tends to be. Therefore, the porosity of the reflective region 40r around the light-transmitting region 40t may be higher than the porosity of the outer portion. This allows the reflective region 40r to efficiently reflect the fluorescence emitted within the light-transmitting region 40t and directed toward the reflective region 40r. The reflective region 40r may also have the function of dissipating heat generated in the light-transmitting region 40t due to irradiation with a collimated beam to the outside. This reduces degradation of the phosphor in the light-transmitting region 40t. The reflective region 40r may be made primarily of ceramic or metal. The wavelength converting section 40 only needs to have at least the light-transmitting region 40t, and may not necessarily have the reflective region 40r.

[0028] The wavelength conversion unit 40 may further include a heat dissipation member on at least one of the upper and lower surfaces to efficiently dissipate heat to the outside. Since a gap between the wavelength conversion unit 40 and the heat dissipation member reduces heat dissipation, a member such as grease or a dielectric film may be provided to fill the gap between the wavelength conversion unit 40 and the heat dissipation member.

[0029] The wavelength conversion unit 40 may further include a filter on the light incident surface 40s1 side of the light-transmitting region 40t that transmits the collimated beam and reflects the fluorescence emitted from the phosphor. This reduces the possibility that the fluorescence will be emitted toward the aspherical lens 30, allowing the fluorescence to be efficiently emitted from the light exit surface 40s2 of the light-transmitting region 40t. The filter may be formed, for example, from a dielectric multilayer film in which high-refractive-index layers and low-refractive-index layers are alternately stacked. The dielectric multilayer film reflects light in a specific wavelength range at approximately 100% and transmits light other than that. The dielectric multilayer film may be designed so that this specific wavelength range includes part or all of the wavelength range of the fluorescence spectrum.

[0030] The size of the light-transmitting region 40t in the wavelength converting unit 40 in the X and Y directions is, for example, 0.5 μm to 100 μm, and the thickness in the Z direction is, for example, 0.1 mm to 10 mm. The gap in the Z direction between the aspherical lens 30 and the wavelength converting unit 40 is, for example, 1 mm to 300 mm. In this specification, the gap between components may be rephrased as the shortest distance between the components.

[0031] The housing 50 in this embodiment may be, for example, a cylinder with a circular cross section. The housing 50 may also be a rectangular tube with a polygonal cross section, or a dome. The height of the housing 50 in the Z direction is determined by the sum of the thickness of the light source 20, the gap between the light source 20 and the aspherical lens 30, the thickness of the aspherical lens 30, and the gap between the aspherical lens 30 and the wavelength conversion unit 40. The relationship between the height of the housing 50 in the Z direction and each component is not limited to this and can be adjusted as appropriate. For example, components other than those mentioned above may be housed in the housing 50, and the traveling direction of the collimated beam 20b may be changed midway by disposing a reflecting mirror, etc.

[0032] Next, reference is made to Figures 3A and 3B. Figures 3A and 3B are side views, viewed from the X and Y directions, respectively, that schematically illustrate how a collimated beam 20b emitted from a light source 20 is converged by an aspherical lens 30 and enters a light incident surface 40s1 of a light-transmitting region 40t in the wavelength conversion unit 40. In Figures 3A and 3B, a portion of a housing 50 is depicted by a dashed line for ease of explanation. A cover portion 50c of the housing 50 has a through-hole 50o that allows the multiple collimated beams 20b converged by the aspherical lens 30 to pass through, and supports the wavelength conversion unit 40. The wavelength conversion unit 40 is supported by an edge portion 50e of the through-hole 50o. A support 50s of the housing 50 protrudes inward from a sidewall portion and supports the aspherical lens 30. A portion of a flat portion 30f of the aspherical lens 30 is bonded to the support 50s. The area between the fine dashed lines represents the beam width of collimated beam 20b. The beam width of collimated beam 20b shown in Fig. 3A is wide in the column direction (Y direction), while the beam width of collimated beam 20b shown in Fig. 3B is narrow in the row direction (X direction). The reason for this will be explained later. The open arrows represent mixed light of collimated beam 20b passing through light-transmitting region 40t and fluorescence emitted from the phosphor contained in light-transmitting region 40t.

[0033] In the examples shown in FIGS. 3A and 3B , two and five collimated beams 20b are converged by the aspherical lens 30 and incident on the light incident surface 40s1 of the light-transmitting region 40t, respectively. Portions of the optical axes of the collimated beams 20b are represented by dashed lines spaced wider than the dashed lines representing the beam widths of the collimated beams 20b. The focal point F of the aspherical lens 30 corresponds to the point where the optical axes of the collimated beams 20b converge. However, in reality, the positions of the collimated beams 20b may differ, and the beam diameters of the collimated beams 20b may vary. Therefore, not all of the collimated beams 20b necessarily converge at a single point. Even if there were no positional deviation and the beam diameters were the same, the width at which all of the collimated beams 20b can be converged is subject to the diffraction limit of light, so it is safe to assume that all of the collimated beams 20b will not converge at the point shown in the figure. In this specification, for the sake of convenience, the light-converging point F is simplified to one point.

[0034] As shown in FIGS. 3A and 3B , the light incident surface 40s1 of the light-transmitting region 40t is perpendicular to the optical axis of the aspherical lens 30 and is positioned away from the focal point F of the aspherical lens 30. The distance between the light incident surface 40s1 of the light-transmitting region 40t and the focal point F is, for example, 1 mm or more and 20 mm or less. If the light incident surface 40s1 of the light-transmitting region 40t intersects with the optical axis of the aspherical lens 30, the light incident surface 40s1 of the light-transmitting region 40t can be illuminated with a plurality of converged collimated beams 20b without changing the traveling direction of the collimated beams 20b using a reflecting mirror or the like. In the example shown in FIGS. 3A and 3B , the focal point F of the aspherical lens 30 is positioned between the aspherical lens 30 and the light incident surface 40s1 of the light-transmitting region 40t. All of the multiple collimated beams 20b diverging from the focal point F are incident on the light incident surface 40s1 of the light-transmitting region 40t without being obstructed by the edge portion 50e of the through-hole 50o. The focal point F may be located within the light-transmitting region 40t. As another example, the light incident surface 40s1 of the light-transmitting region 40t may be located between the aspherical lens 30 and the focal point F.

[0035] When the light incident surface 40s1 of the light-transmitting region 40t is deviated from the focal point F of the aspherical lens 30, the light incident surface 40s1 can be illuminated with a plurality of defocused collimated beams 20b. This allows the light density of the collimated beams 20b on the light incident surface 40s1 to be reduced compared to when the light incident surface 40s1 of the light-transmitting region 40t is aligned with the focal point F of the aspherical lens 30.

[0036] <Convex portion 30c of aspherical lens 30> Next, we will explain the aspherical shape of the surface of the convex portion 30c of the aspherical lens 30. The surface shape of the convex portion 30c can be defined by the conic constant. If the conic constant is k and the curvature at the apex of the aspherical lens 30 is c=1 / R (R is the radius of curvature), then the coordinates (X, Y, Z)=(x, y, z) on the curved surface of the aspherical lens 30, with the apex of the aspherical lens 30 as the origin, satisfy the following formula (1):

number

[0037] z represents the distance in the Z direction between the XY plane containing the vertex of the lens and the curved surface of the lens, and r = (x 2 +y 2 ) 1 / 2 represents the distance in the XY plane between the curved surface of the lens and the optical axis of the aspherical lens 30. 2i (2i=2, . . . , n) represents the aspherical coefficients.

[0038] First, a 2i = 0. In this case, equation (1) corresponds to one of the solutions of equation (2) below.

number

[0039] From equation (2), a 2i It can be seen that equation (1) when = 0 represents any of the following curved surfaces: hyperboloid, paraboloid, sphere, and ellipsoid.

[0040] Next, refer to FIG. 4. FIG. 4 is a graph plotting the surface of the lens shown in Equation (1) when a 2i = 0. The conic constants were selected in 0.5 increments from k = -1.5 to k = +1.5. The solid line represents the function of Equation (1), and the dashed line represents the part of the function of Equation (2) other than Equation (1). The relationship between the conic constant k and the surface of the graph is as follows. The surface of the graph is a hyperboloid when k < -1, a paraboloid when k = -1, an ellipsoid with the r direction as the minor axis and the z direction as the major axis when -1 < k < 0, a sphere when k = 0, and an ellipsoid with the r direction as the major axis and the z direction as the minor axis when k > 0. The radius of curvature of the surface of the graph becomes larger than the radius of curvature R when k < 0, equal to the radius of curvature R when k = 0, and smaller than the radius of curvature R when k > 0 as the distance r increases. The surface of the lens of the aspherical lens 30 corresponds to the surface of the graph including the origin represented by the solid line. The convex portion 30c of the aspherical lens 30 in the present embodiment has a surface other than the conic constant k = 0.

[0041] Next, referring to FIG. 5, the effect obtained by the convex portion 30c in the aspherical lens 30 will be described. FIG. 5 is a diagram showing the calculation result of the intensity distribution of the 2-row 5-column irradiation collimated beam converged by the convex portion 30c with a conic constant k = +0.5. For the calculation, OpticStudio, an optical simulation software from Zemax, was used. The calculation conditions are as follows. However, the present disclosure is not limited to the light-emitting device with the following calculation conditions. The spot of the collimated beam 20b before entering the convex portion 30c has an elliptical shape in the XY plane, the minor diameter in the X direction is 1.0 mm, and the major diameter in the Y direction is 4.9 mm. The spot of the collimated beam 20b is at 1 / e of the peak intensity 2(e is Napier's constant). The center-to-center spacing between two adjacent collimated beams 20b in the row direction (X direction) is 3.5 mm, and the center-to-center spacing in the column direction (Y direction) is 5.9 mm. The thickness of the aspherical lens 30 in the Z direction is 20 mm. The radius of curvature R of the convex portion 30c at the origin is 26.605 mm. The refractive index of the aspherical lens 30 is n = 1.52308, and the refractive index of the periphery of the aspherical lens 30 is n = 1. When k = +0.5, the distance from the flat portion 30f of the aspherical lens 30 to the focal point F is 36.2 mm. The distance between the light incident surface 40s1 of the light-transmitting region 40t and the focal point F of the aspherical lens 30 is 9.8 mm. The focal point F is located between the light incident surface 40s1 of the light-transmitting region 40t and the aspherical lens 30.

[0042] As shown in FIG. 5, the intensity distributions of the four collimated illumination beams at the edges of the row direction (X direction) are shaped to extend toward the four corners of the light incident surface 40s1 of the rectangular light-transmitting region 40t. Thus, the multiple collimated beams 20b include at least one pair of outer collimated beams irradiated onto the corners of the light incident surface 40s1 and one or more inner collimated beams sandwiched between the outer collimated beams. Compared to the intensity distribution shown in FIG. 1B using a spherical lens, the use of an aspherical lens 30 reduces the concentration of the collimated illumination beams 20b. In other words, the aspherical lens 30 has a shape that causes the outer collimated beams to diverge more than the inner collimated beams. As mentioned above, the proportion of fluorescence increases at the edges of the light-transmitting region 40t, particularly at the four corners, due to reflection by the reflective region 40r. Distributing the intensity distribution of the irradiated collimated beam toward the edge portions, particularly the four corners, of the light incident surface 40s1 of the light-transmitting region 40t increases the proportion of collimated beams 20b in those areas compared to when the beam is not dispersed. As a result, the color of the light emitted from the edge portions, particularly the four corners, of the light exit surface 40s2 of the light-transmitting region 40t can be made closer to the color of the light emitted from the center portion of the light exit surface 40s2. This reduces color unevenness in the mixed light emitted from the light exit surface 40s2 of the light-transmitting region 40t. The degree of divergence of the outer collimated beam can be set so that the beam width of the outer collimated beam in the divergence direction is 1.1 times or more, preferably 1.3 times or more, the beam width of the inner collimated beam. This further reduces color unevenness. Furthermore, since the optical density of the outer collimated beam decreases as it diverges, it is preferable that the degree of divergence be such that the beam width of the outer collimated beam is 2.5 times or less that of the inner collimated beam. The beam width in the divergence direction is, for example, the beam width in the major axis direction of a substantially elliptical beam. It is more preferable that the inner collimated beam used for comparing the beam width is the collimated beam that is closest to the center of the aspherical lens among the multiple collimated beams 20b when passing through the aspherical lens.

[0043] Next, referring to FIG. 6, the relationship between the conic constant k of the lens and the intensity distribution of the irradiated collimated beam will be described. FIG. 6 is a diagram showing the calculation results of the intensity distribution of a 2-row 5-column irradiated collimated beam converged by lenses with various conic constants. As the conic constants, k = -1.5 (hyperboloid), k = -1.0 (paraboloid), k = -0.5 (ellipsoid), k = 0 (sphere), k = +1.0 (ellipsoid), and k = +1.5 (ellipsoid) were selected. Based on the conic constant k = 0 (sphere), the intensity distribution of the irradiated collimated beam converges to the central portion of the light incident surface 40s1 of the light transmission region 40t as the conic constant is negative (k < 0) and smaller, and disperses to the end portions of the light incident surface 40s1 of the light transmission region 40t, particularly the four corners, as the conic constant is positive (k > 0) and larger. The conic constant k of the aspherical lens 30 in the present disclosure is designed within the range of -15 < k < 0 or 0 < k < +6.

[0044] In the example described above, the shape of the surface of the convex portion 30c of the aspherical lens 30 was designed by changing the conic constant k, but it may be designed by changing at least one of the conic constant k, the curvature c, and the aspherical coefficient a 2i of them.

[0045] Two representative methods of modulating the intensity distribution of the irradiated collimated beam can be considered. One is a method of converging a plurality of collimated beams 20b with at least one different center-to-center distance between the beams by a spherical lens. The other is a method of converging a plurality of collimated beams 20b arranged at equal intervals as in the present disclosure by an aspherical lens 30. According to the analysis of the inventor, the latter can reduce the size of the light source 20, and accordingly, the size of the aspherical lens 30 can be reduced, so that the light emitting device 100 can be made smaller.

[0046] Furthermore, the light source 20 is configured to include multiple semiconductor light-emitting elements 25 in a single package, which also contributes to the miniaturization of the light-emitting device 100. This is because the shortest distance between the collimated beams 20b emitted from two adjacent semiconductor light-emitting elements 25 in a single package is easier to make shorter than the shortest distance between the collimated beams 20b emitted from two adjacent packages when the light source 20 is configured with multiple packages. In other words, by including multiple semiconductor light-emitting elements 25 in a single package, the irradiation range of the multiple collimated beams 20b can be made smaller than when the same number of semiconductor light-emitting elements 25 are distributed across multiple packages. This allows the size of the aspherical lens 30 to be reduced, thereby further miniaturizing the light-emitting device 100.

[0047] The desired intensity distribution of the irradiated collimated beam can be determined by the shape of the light incident surface 40s1 of the light-transmitting region 40t. Therefore, the aspherical shape of the convex portion 30c of the aspherical lens 30 can be appropriately designed according to the shape of the light incident surface 40s1 of the light-transmitting region 40t. For example, when the light incident surface 40s1 of the light-transmitting region 40t is circular, elliptical, or oval, an aspherical lens 30 having a convex portion 30c with a negative Conic constant (k<0) may potentially reduce color unevenness in the mixed light. An oval shape refers to a shape similar to a circle or ellipse, a non-intersecting closed curve, and a shape that is line-symmetric at at least one point. When the collimated beams 20b are arranged in a matrix, the results shown in Figure 6 indicate that the corners of the matrix-arranged collimated beams 20b tend to shrink toward the center as the Conic constant (k<0) increases in absolute value. Furthermore, it can be said that as the absolute value of the conic constant becomes larger when the conic constant is positive (k>0), the four corners of the matrix-like collimated beam 20b tend to expand in a direction away from the center. When the light incident surface 40s1 of the light-transmitting region 40t is circular, elliptical, or oval, the aspherical shape of the surface of the convex portion 30c may be a curved surface with a conic constant of -1.0 or less (k≦-1.0). When the light incident surface 40s1 of the light-transmitting region 40t is rectangular, the aspherical shape of the surface of the convex portion 30c may be a curved surface with a conic constant of 0.5 or more (k≧0.5).

[0048] In addition to changing the aspherical shape of the surface of the convex portion 30c of the aspherical lens 30, the intensity distribution of the irradiated collimated beam may be modulated by changing the distance between the light incident surface 40s1 of the light-transmitting region 40t and the focal point F of the aspherical lens 30.

[0049] <Example of internal configuration of light source 20> Next, an example of the internal configuration of light source 20 will be described with reference to Fig. 7A. Fig. 7A is a diagram of light source 20 shown in Fig. 2B, in which frame 22 and cover 23 are omitted. For ease of explanation, base 21 and optical element 24 are depicted as being farther apart than they actually are.

[0050] On the main surface 21s of the base 21, the semiconductor light-emitting elements 25 are arranged in two rows and five columns via submounts 26. The light-emitting end faces of the semiconductor light-emitting elements 25 arranged in one row face the light-emitting end faces of the semiconductor light-emitting elements 25 arranged in the other row. In this manner, the semiconductor light-emitting elements 25 are arranged in a matrix of one to two or more rows or two to one or more columns along a plane (XY plane) perpendicular to the optical axis of the aspherical lens 30. The submount 26 can adjust the height of the semiconductor light-emitting elements 25 in the Z direction. The center-to-center distance between adjacent semiconductor light-emitting elements 25 is, for example, 0.85 mm or more. This reduces the influence of heat generated by the semiconductor light-emitting elements 25 on each other. On the other hand, considering the miniaturization of the light source 20, it is desirable that the center-to-center distance between adjacent semiconductor light-emitting elements 25 be, for example, 2.5 mm or less. In the example shown in FIG. 7A, the semiconductor light-emitting elements 25 are arranged at equal intervals in the row direction and at equal intervals in the column direction, but they do not have to be arranged at equal intervals. As described above, it is also possible to modulate the intensity distribution of the irradiated collimated beam by adjusting the center-to-center distance between adjacent semiconductor light-emitting elements 25. In addition, the semiconductor light-emitting elements 25 may be arranged in only one column, or in a matrix of multiple rows and columns.

[0051] Light reflecting members 27 are arranged in two rows and five columns on the main surface 21s of the base 21. A reflecting surface 27r provided on the inclined surface of the light reflecting member 27 faces the light-emitting end surface of the semiconductor light-emitting element 25 and reflects light emitted from the semiconductor light-emitting element 25. The angle formed between the reflecting surface 27r of the light reflecting member 27 and the main surface 21s of the base 21 is determined by the relative positions of the semiconductor light-emitting elements 25 and the optical element 24. In the example shown in FIG. 7A , this angle is 45 degrees, but it may be an angle other than 45 degrees. Light emitted from the semiconductor light-emitting elements 25 arranged in two rows is reflected by the reflecting surface 27r of the light reflecting member 27 in a direction away from the main surface 21s of the base 21 and enters the optical element 24. Of the two rows of semiconductor light-emitting elements 25, the semiconductor light-emitting elements 25 in one row emit light in the +Y direction, and the semiconductor light-emitting elements 25 in the other row emit light in the -Y direction. The +Y direction corresponds to the direction of the arrow in FIG. 7A, and the −Y direction corresponds to the direction opposite to the arrow in FIG. 7A.

[0052] The light reflecting member 27 may be mainly made of, for example, glass such as quartz or BK7 (borosilicate glass), a metal such as aluminum, or Si. The reflecting surface 27r of the light reflecting member 27 is desirably formed from a material having a relatively high reflectance for the light emitted by the semiconductor light emitting element 25. This material is a metal or a dielectric multilayer film. The light reflectance of the reflecting surface 27r may be, for example, 70% or more, or may be 90%, at the peak wavelength of the light emitted by the semiconductor light emitting element 25. The light reflecting member 27 may have a plurality of light reflecting surfaces. The light source 20 may further include a light reflecting member in addition to the light reflecting member 27.

[0053] The optical element 24 includes collimating lenses 24l arranged in 2 rows and 5 columns. The collimating lenses 24l are provided at positions where the light emitted from the semiconductor light emitting elements 25 passes through the collimating lenses 24l. The optical element 24 emits 2 rows and 5 columns of collimated beams from the collimating lenses 24l arranged in 2 rows and 5 columns.

[0054] The collimating lens 24l in the optical element 24 may be made of, for example, at least one of glass, quartz, sapphire, transparent ceramics, and plastic. The size of the optical element 24 in the X and Y directions is, for example, 15 mm or more and 20 mm or less, and the thickness in the Z direction is, for example, 2.0 mm or more and 5.0 mm or less.

[0055] The number and arrangement of the semiconductor light-emitting elements 25 are not limited to those shown in Fig. 7A. The number of semiconductor light-emitting elements 25 may be plural. To reduce the size of the light source 20, the number may be, for example, 30 or less. The same applies to the collimating lens 24l and the light reflecting member 27 in the optical element 24.

[0056] The semiconductor light-emitting element 25 is, for example, a laser diode. A laser diode emits coherent light. The laser diode has a structure in which an n-side cladding layer, an active layer, and a p-side cladding layer are arranged in this order. The laser diode further includes an electrode (n-side electrode) located on the n-side cladding layer side and an electrode (p-side electrode) located on the p-side cladding layer side. The electrodes may be formed of a light-transmitting conductive material and used as cladding layers. Laser light is emitted from the laser diode by applying a voltage between the n-side electrode and the p-side electrode to pass a current equal to or greater than a threshold. In FIG. 7A, the laser light is emitted from the end face of the semiconductor light-emitting element 25 in a direction parallel to the Y direction. The emitted laser light spot has an elliptical far-field pattern with its major axis in the Z direction and its minor axis in the X direction. The laser diode can emit laser light of any color in the visible range, for example. When light outside the visible range is used as part of the mixed light, the laser diode may emit laser light outside the visible range, such as ultraviolet light. 7A, all of the semiconductor light-emitting elements 25 may emit laser light of the same wavelength, or at least one of the semiconductor light-emitting elements 25 may emit laser light of a different wavelength. In order to reduce color unevenness, it is preferable that all of the light from the semiconductor light-emitting elements 25 be the same color.

[0057] When a YAG phosphor is used as the phosphor, for example, a laser diode that emits blue laser light is used. The emission peak wavelength of the blue light is preferably in the range of 420 nm to 480 nm, and more preferably in the range of 440 nm to 460 nm. An example of a laser diode that emits blue laser light is a semiconductor laser element containing a nitride semiconductor. Examples of nitride semiconductors that can be used include GaN, InGaN, and AlGaN. By changing the composition, a semiconductor laser element containing a nitride semiconductor can emit light from the ultraviolet to the visible region.

[0058] The semiconductor light-emitting element 25 may be hermetically sealed in a package as needed. The base 21, the frame 22, and the lid 23 constitute a package that hermetically seals the semiconductor light-emitting element 25. In this case, if the semiconductor light-emitting element 25 is a laser diode, the light source 20 can be said to be a semiconductor laser package. If the semiconductor light-emitting element 25 is a laser diode that emits laser light with a relatively short wavelength (e.g., a wavelength of approximately 480 nm or less), if the emission end face of the laser diode is exposed to the outside air, end face deterioration may progress during operation due to dust collection effects, etc. Such end face deterioration may lead to a decrease in the optical output of the laser diode. It is desirable to hermetically seal the laser diode to improve its reliability and extend its lifespan.

[0059] The semiconductor light emitting element 25 may include a light emitting diode (LED) that emits incoherent light. When combined with a lens, laser light can reduce light loss, so the semiconductor light emitting element 25 is preferably a laser diode.

[0060] Like the substrate 10 in the light-emitting device 100, the base 21 is preferably made of a material with relatively high thermal conductivity in order to quickly dissipate heat generated by the plurality of semiconductor light-emitting elements 25 to the outside. Similarly, the submount 26 is preferably made of a material with high thermal conductivity. Examples of the main material of the base 21 include metals such as Cu, and ceramics such as aluminum nitride and silicon carbide. Examples of the main material of the submount 26 include aluminum nitride and silicon carbide.

[0061] The lower surface of the semiconductor light-emitting element 25 is bonded to the upper surface of the submount 26. Therefore, when the side surface of the semiconductor light-emitting element 25 is the light-emitting surface, the semiconductor light-emitting element 25 emits light in a direction parallel to the main surface 21s of the base 21. For example, the semiconductor light-emitting element 25 is fixed to the submount 26, which is provided with a metal film, via a conductive layer such as Au—Sn. The semiconductor light-emitting element 25 may be configured to emit light directly in the Z direction. In this case, the light-reflecting member 27 is not required. A conductive layer for wire connection may be provided in areas of the submount 26 other than the area where the semiconductor light-emitting elements 25 are provided, to facilitate electrical connection via wire between the multiple semiconductor light-emitting elements 25 and the lead terminals 22l on the frame 22.

[0062] Next, with reference to FIGS. 7B and 7C, differences in the beam widths of the collimated beams 20b shown in FIGS. 3A and 3B will be described. Here, the semiconductor light-emitting element 25 includes a laser diode. FIGS. 7B and 7C are cross-sectional views in the YZ plane and the XZ plane, respectively, that schematically illustrate how the laser light emitted from the semiconductor light-emitting element 25 is reflected by the reflecting surface 27r of the light-reflecting member 27 and collimated by the collimating lens 24l of the optical element 24. The lid 23 includes a light-transmitting member 23t that closes the opening 23o and a spacer 23s that forms a gap between the light-transmitting member 23t and the optical element 24. As described above, the laser light emitted from the semiconductor light-emitting element 25 is largely expanded in the Z direction but not so much in the X direction. Therefore, as shown in FIG. 7B, when the laser light that is largely expanded in the Z direction is reflected upward and collimated, the beam width of the collimated beam 20b in the Y direction becomes wider. 7C, when laser light that does not diverge much in the X direction is reflected upward and collimated, the beam width of collimated beam 20b in the X direction does not diverge much. Therefore, the spot of collimated beam 20b emitted in the Z direction from optical element 24 has an elliptical shape in the XY plane with the major axis in the Y direction and the minor axis in the X direction. Note that the far-field pattern of laser light emitted from semiconductor light-emitting element 25 is not limited to the shape described here, and may have the major and minor axes reversed, for example.

[0063] (Modification of light-collecting part having aspherical surface) Next, a modified example of a light-collecting unit having an aspherical surface according to the present disclosure will be described with reference to FIGS. 8A and 8B. FIGS. 8A and 8B are side views, viewed from the Y direction, that schematically show how a collimated beam 20b emitted from a light source 20 is converged by a parabolic reflecting mirror 31 in the modified example and incident on a light-incident surface 40s1 of a light-transmitting region 40t in a wavelength converting unit 40. In FIGS. 8A and 8B, the substrate 10 and the housing 50 are omitted. The parabolic reflecting mirror 31 in the modified example has a parabolic reflecting surface 31m. The reflecting surface 31m reflects light traveling parallel to the axis 31a of the parabolic surface (Z direction) and converges it to a focusing point F on the axis 31a. It is not necessary for all portions of the reflecting surface 31m shown in FIGS. 8A and 8B to be present; only the portions on which light strikes are required. There are no limitations on the shape of the portions of the parabolic reflecting mirror 31 other than the reflecting surface 31m. 8A and 8B, the light source 20 emits collimated beams 20b arranged in 2 rows and 5 columns in the Z direction. The light incident surface 40s1 of the light-transmitting region 40t is perpendicular to the optical axis of the middle beam of the five collimated beams 20b reflected by the reflecting surface 31m of the parabolic reflecting mirror 31.

[0064] In the example shown in FIG. 8A, the center beam is reflected by the reflecting surface 31m in the X direction. The mixed light represented by the hollow arrow is emitted in the X direction from the light emitting surface 40s2 of the light-transmitting region 40t. In the example shown in FIG. 8B, the light source 20 is positioned farther from the axis 31a than in the example shown in FIG. 8A. In the example shown in FIG. 8B, the collimated beam 20b emitted from the light source 20 also converges at the focusing point F. The center beam is reflected obliquely upward by the reflecting surface 31m. The mixed light is emitted obliquely upward from the light emitting surface 40s2 of the wavelength converting unit 40. Note that, when the light source 20 is positioned closer to the axis 31a than in the example shown in FIG. 8A, the mixed light is emitted obliquely downward from the light emitting surface 40s2 of the wavelength converting unit 40.

[0065] 8A and 8B, the light-converging point F is located between the parabolic reflecting mirror 31 and the light-incident surface 40s1 of the light-transmitting region 40t, but the light-incident surface 40s1 of the light-transmitting region 40t may be located between the aspherical lens 30 and the light-converging point F. The light-converging point F may also be located inside the light-transmitting region 40t.

[0066] The reflecting surface 31m in the modified example does not need to have a parabolic shape, and may have an aspherical shape such as a hyperbolic or ellipsoidal shape depending on the application. Even if the light collecting section having an aspherical surface in the present disclosure is an aspherical reflecting mirror such as the parabolic reflecting mirror 31, it is possible to reduce color unevenness in the mixed light. [Industrial Applicability]

[0067] The light emitting device of the present disclosure can be used in various light sources, such as lighting fixtures, headlamps for vehicles such as automobiles, projector light sources, and endoscope light sources. [Explanation of symbols]

[0068] 10 Substrate 10s Main surface of the board 20 light source 20b Collimated beam 21 Base 21s Main surface of base 22 Frame 22l Lead terminal on the frame 23 Lid 24 Optical Elements Collimating lenses in 24l optical elements 25 Semiconductor light emitting element 26 Submount 27 Light-reflecting member 27r Reflective surface of light-reflecting member 30 Aspherical Lenses 30c convex part 30f flat plate part 31 Parabolic reflector 31a Paraboloid axis 31m reflective surface 40 Wavelength conversion unit 40r reflective area 40s1 Light incidence surface 40s2 Light exit surface 40t transparent area 50 cabinets 50c lid part 50e Edge 50o through hole 50s Support 100 Light-emitting device

Claims

1. A plurality of semiconductor light emitting elements; an optical element that collimates the light emitted from each of the plurality of semiconductor light emitting elements and outputs a plurality of collimated beams; a parabolic or aspherical reflective surface that reflects the plurality of collimated beams to converge the plurality of collimated beams; a light-transmitting region having a light incident surface located between the reflecting surface and a light-condensing point where light reflected by the reflecting surface converges, or on the opposite side of the reflecting surface across the light-condensing point; Equipped with Light-emitting device.

2. A plurality of semiconductor light-emitting elements; an optical element that collimates the light emitted from each of the plurality of semiconductor light emitting elements and outputs a plurality of collimated beams; an aspherical reflective surface that reflects the plurality of collimated beams to converge the plurality of collimated beams; a light-transmitting region having a light incident surface located between the reflecting surface and a light-condensing point where light reflected by the reflecting surface converges, or on the opposite side of the reflecting surface across the light-condensing point; Equipped with the aspherical shape of the reflecting surface is designed according to the shape of the light incident surface of the light-transmitting region; Light-emitting device.

3. The aspherical shape is a parabolic shape. The light emitting device according to claim 2 .

4. the plurality of collimated beams are parallel to one another; The light emitting device according to claim 1 .

5. The plurality of semiconductor light emitting elements are arranged in a matrix of one to two or more rows or two to one or more columns. The light emitting device according to claim 1 .

6. the plurality of semiconductor light emitting elements are a plurality of laser diodes, further comprising a package that hermetically seals the plurality of laser diodes; The light emitting device according to claim 1 .

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