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] Conventionally, 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, a phosphor that emits yellow fluorescence is excited by blue light emitted from a semiconductor light emitting element, and the blue light passing through a phosphor-containing portion is mixed with the yellow fluorescence emitted from the phosphor to obtain a 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 passing through the phosphor-containing portion and 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 aspheric 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 includes a phosphor that is excited by the plurality of collimated beams converged by the focusing section. Effect of the Invention

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

[0007] [Figure 1A] FIG. 1A is a perspective view that illustrates a wavelength conversion section 40 having a light-transmitting region 40t that contains a phosphor and a reflective region 40r that surrounds it. [Figure 1B] FIG. 1B is a diagram showing a calculation result of the intensity distribution on a light incident surface 40s1 of a light-transmitting region 40t of a 2-row, 5-column collimated beam converged by a spherical lens. [Figure 1C] FIG. 1C is a diagram illustrating a schematic distribution of colors of mixed light emitted from a light exit surface 40s2 of a light-transmitting region 40t. [Figure 2A] FIG. 2A is a perspective view diagrammatically illustrating a light emitting device 100 according to an embodiment of the present disclosure. [Figure 2B] FIG. 2B is a perspective view that illustrates a schematic view of the inside of the light emitting device 100 illustrated in FIG. 2A. [Figure 3A] FIG. 3A is a side view seen from the X direction, which diagrammatically illustrates how collimated beam 20b emitted from light source 20 is converged by aspheric lens 30 and enters light incident surface 40s1 of light-transmitting region 40t in wavelength conversion unit 40. FIG. [Figure 3B]3B is a side view seen from the Y direction, which diagrammatically shows how collimated beam 20b emitted from light source 20 is converged by aspheric lens 30 and enters light incident surface 40s1 of light-transmitting region 40t in wavelength conversion unit 40. FIG. [Figure 4] FIG. 4 is a graph plotting the lens curve shown in equation (1). [Diagram 5] FIG. 5 is a diagram showing the calculated intensity distribution of a 2-row, 5-column collimated illumination beam converged by an aspheric lens 30 with a Conic constant k=+0.5. [Figure 6] FIG. 6 shows the calculated intensity distribution of a 2-row, 5-column 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] FIG. 7B is a cross-sectional view in the YZ plane that typically illustrates 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. As shown in FIG. [Figure 7C] FIG. 7C is a cross-sectional view in the XZ plane that typically illustrates 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. As shown in FIG. [Figure 8A] Figure 8A is a side view viewed from the Y direction, showing typically 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, showing typically 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 showing a schematic diagram of a spectrum of excitation light of a single wavelength and a spectrum of fluorescent light. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (Fluorescence spectrum) Before describing the embodiments of the present disclosure, a description will be given of 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.

[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 being transmitted through the phosphor or being reflected by the phosphor. Therefore, a mixture of the excitation light transmitted through the phosphor and the fluorescence emitted from the phosphor is obtained. For example, when a blue laser beam with a wavelength of 455 nm is used to excite YAG (Yttrium Aluminum When a (CuO) 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 equipment. 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 the excitation light and the phosphor.

[0010] (Findings on which the embodiments of the present disclosure are based) Next, the findings on which the embodiments of the present disclosure are based will be described with reference to Figures 1A to 1C. When a phosphor is irradiated with excitation light to obtain a mixed light of the excitation light transmitted through the phosphor and the fluorescence emitted from the phosphor, the phosphor can be used in the following form.

[0011] FIG. 1A is a perspective view showing a wavelength conversion unit 40 having a light-transmitting region 40t containing a phosphor and a reflective region 40r surrounding the light-transmitting region 40t. The light-transmitting region 40t includes an exposed light-entering surface 40s1 and a light-emitting surface 40s2 that are parallel to each other. The light-transmitting region 40t may be, for example, ceramics containing a phosphor, that is, phosphor ceramics. Since the fluorescence emitted by the phosphor is substantially undistributed, in the phosphor ceramics, a part of the fluorescence is directed toward the reflective region 40r and is reflected by the reflective region 40r. The phosphor ceramics are formed, for example, from an inorganic binder and a phosphor. The reflective region 40r may be formed, for example, from ceramics. In the example shown in FIG. 1A, the light-transmitting region 40t is formed mainly from a binder of a YAG phosphor and aluminum oxide, and the reflective region 40r is formed mainly from aluminum oxide. The light-transmitting region 40t and the reflective region 40r containing the same aluminum oxide have high adhesion.

[0012] As an excitation light source for exciting the YAG phosphor contained in the light-transmitting region 40t, for example, a semiconductor laser package that emits multiple blue collimated beams can be used. If multiple collimated beams are converged by one condenser lens and the converged multiple beams are irradiated onto the light incident surface 40s1 of the light-transmitting region 40t, mixed light can be obtained. A collimated beam means a beam that is collimated so that the beam diameter is constant in the traveling direction of the beam. However, the beam diameter may not be strictly constant. In addition, when a collimated beam is converged by a condenser lens, the beam diameter gradually narrows, and after it becomes a minimum at the beam waist, it gradually expands. In this specification, for the sake of simplicity, the term "collimated beam" also includes the beam after the collimated beam has passed through the condenser lens.

[0013] FIG. 1B is a diagram showing the calculation result of the intensity distribution on the light incidence surface 40s1 of the light-transmitting region 40t of the 2-row, 5-column irradiated collimated beam converged by the spherical lens. In FIG. 1B, the light intensity is shown relatively, with white being 0% and black being 100%, and the intensity is shown by shading. Hereinafter, the intensity distribution on the light incidence surface 40s1 of the collimated beam irradiated to the light-transmitting region 40t is simply referred to as the "intensity distribution of the irradiated collimated beam". Details of the calculation conditions will be described later. The area surrounded by a black rectangular frame represents the light incidence surface 40s1 of the light-transmitting region 40t. The light incidence 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 part of the light incidence surface 40s1 of the light-transmitting region 40t is mainly irradiated. 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 large, and the edge portions of the light incident surface 40s1, especially the four corners, are hardly irradiated. The phosphor excited by the collimated beams incident on the light-transmitting region 40t emits fluorescence. Therefore, white light, which is a mixture of blue light passing through the light-transmitting region 40t and 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 unevenness.

[0014] FIG. 1C is a diagram showing a schematic distribution of colors 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 lot 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, especially the four corners, resulting in large color unevenness. The following reasons are considered for this. A part of the fluorescence emitted at the location where the four collimated beams at the end of the row direction (X direction) are irradiated heads toward the reflection region 40r, is reflected by the reflection region 40r, and is then emitted from the light exit surface 40s2. The fluorescence is reflected by two mutually perpendicular surfaces at the corners of the reflection region 40r. 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 believe that the cause of color unevenness is the intensity distribution of the collimated irradiation beam on the light incident surface of the light-transmitting region, and have come up with a novel light-emitting device that can reduce color unevenness. This light-emitting device includes a focusing unit having an aspheric surface that converges multiple collimated beams emitted from a light source. The shape of this aspheric surface is appropriately designed so that the intensity distribution of the converged collimated irradiation beam reduces color unevenness of the mixed light. The 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 is intended to embody the technical idea 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 the components shown in each drawing may be exaggerated to clarify the description.

[0017] In this specification, the term "a component is placed 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 placed directly on the 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 the surface. Note that when it is specified that a component is placed directly on a surface, the word "directly" is used. When it is not specified that a component is placed directly, it indicates that either is acceptable.

[0018] <Example of the configuration of a 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 showing a light emitting device 100 according to an embodiment of the present disclosure. Fig. 2B is a perspective view showing the inside of the light emitting device 100 shown in Fig. 2A. In Fig. 2B, the outline of the housing 50 is shown by a dashed line. For reference, the drawing shows an X direction, a Y direction, and a Z direction that are orthogonal to each other.

[0020] The light emitting device 100 in this embodiment includes a substrate 10 having a main surface 10s, a light source 20 located on the main surface 10s and emitting a collimated beam in two rows and five columns, an aspheric lens 30 having a convex portion 30c for converging the collimated beam, a wavelength conversion unit 40 having a light transmitting region 40t on the optical axis of the aspheric lens 30, and a housing 50 for accommodating the light source 20 and the aspheric 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 arranged with reference to the main 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 has a thickness in the Z direction. The substrate 10 is desirably formed of a material with relatively high thermal conductivity in order 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 more. 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 each of the semiconductor light-emitting elements arranged in two rows and five columns in the light source 20, and outputs two rows and five columns of collimated beams in a direction parallel to the optical axis of the aspheric lens 30 (Z direction). The directions of travel of these collimated beams are parallel to each other. However, the directions of travel do not need to be strictly parallel. In this specification, "parallel" is not limited to "parallel" in the mathematically strict sense. In this specification, "parallel" can tolerate a deviation of 1.5 degrees or less from strictly parallel, for example. If there are multiple collimated beams, the light-transmitting region 40t containing the 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. A suitable wavelength of the collimated beam is selected according to the type of phosphor. The size of the light source 20 in the X direction and the Y direction 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 aspheric 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 does not necessarily have to be 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 be thicker than the convex portion 30c. The light collecting portion having an aspheric surface in this disclosure may be, for example, an aspheric lens 30.

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

[0025] The wavelength conversion unit 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 shape, a circular shape, an elliptical shape, or a shape similar to these.

[0026] The light-transmitting region 40t in the wavelength conversion unit 40 includes a YAG phosphor that is excited by blue light to emit yellow fluorescence, but is not limited thereto, and may include, for example, a first phosphor that is excited by blue light to emit yellow or green fluorescence and a second phosphor that emits red fluorescence. By irradiating the light entrance 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 reflection region 40r in the wavelength conversion unit 40 may be formed mainly of zirconium oxide or titanium oxide in addition to aluminum oxide. The reflection region 40r may contain additives such as yttrium oxide, zirconium oxide, lutetium oxide, or lanthanum oxide to reduce light transmittance. When the reflection region 40r is made of ceramics, the higher the porosity of the reflection region 40r, the higher the light reflectance tends to be. For this reason, the porosity of the reflection region 40r around the light-transmitting region 40t may be made higher than the porosity of the outer portion. This allows the reflection region 40r to efficiently reflect the fluorescence emitted in the light-transmitting region 40t and directed toward the reflection region 40r. The reflection region 40r may also have a function of discharging heat generated in the light-transmitting region 40t by irradiation of a collimated beam to the outside. This allows the deterioration of the phosphor in the light-transmitting region 40t to be reduced. The reflective region 40r may be mainly made of ceramics or metal. The wavelength converting section 40 may not necessarily have the reflective region 40r as long as it has at least the light transmitting region 40t.

[0028] The wavelength conversion unit 40 may further include a heat dissipation member on at least one of the upper and lower surfaces in order 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 that fills the gap between the wavelength conversion unit 40 and the heat dissipation member may be provided.

[0029] The wavelength conversion unit 40 may further include a filter on the light incident surface 40s1 side of the light transmitting region 40t, which transmits the collimated beam and reflects the fluorescence emitted from the phosphor. This reduces the possibility that the fluorescence is emitted toward the aspheric lens 30, so that the fluorescence can be efficiently emitted from the light exit surface 40s2 of the light transmitting region 40t. The filter may be formed of, for example, a dielectric multilayer film in which high refractive index layers and low refractive index layers are alternately stacked. The dielectric multilayer film can reflect light in a specific wavelength range at approximately 100% and transmit other light. 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 or more and 100 μm or less, and the thickness in the Z direction is, for example, 0.1 mm or more and 10 mm or less. The gap in the Z direction between the aspheric lens 30 and the wavelength converting unit 40 is, for example, 1 mm or more and 300 mm or less. In this specification, the gap between parts may be rephrased as the shortest distance between the parts.

[0031] The housing 50 in this embodiment may be, for example, a cylinder having a circular cross section. The housing 50 may be a square tube having 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 these may be housed in the housing 50, and the traveling direction of the collimated beam 20b may be changed midway by arranging a reflecting mirror, etc.

[0032] Next, reference is made to FIG. 3A and FIG. 3B. FIG. 3A and FIG. 3B are side views seen from the X direction and the Y direction, respectively, which show a state in which the collimated beam 20b emitted from the light source 20 is converged by the aspherical lens 30 and is incident on the light incident surface 40s1 of the light-transmitting region 40t in the wavelength conversion unit 40. In FIG. 3A and FIG. 3B, for convenience of explanation, a part of the housing 50 is drawn by a broken line. The cover portion 50c of the housing 50 has a through hole 50o that passes the multiple collimated beams 20b converged by the aspherical lens 30, and supports the wavelength conversion unit 40. The wavelength conversion unit 40 is supported by an edge portion 50e of the through hole 50o. The support 50s of the housing 50 protrudes inward from the side wall portion and supports the aspherical lens 30. A part of the flat plate 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 the collimated beam 20b. The beam width of the collimated beam 20b shown in Fig. 3A is wide in the column direction (Y direction), and the beam width of the collimated beam 20b shown in Fig. 3B is narrow in the row direction (X direction). The reason for this will be described later. The white arrows represent a mixture of the collimated beam 20b transmitted through the light-transmitting region 40t and the fluorescence emitted from the phosphor contained in the light-transmitting region 40t.

[0033] In the examples shown in FIG. 3A and FIG. 3B, two and five collimated beams 20b are converged by the aspherical lens 30 and enter the light incidence surface 40s1 of the light-transmitting region 40t, respectively. A part of the optical axis of the collimated beam 20b is represented by a dashed line with a wider interval than the dashed line representing the beam width of the collimated beam 20b. The light-converging point F of the aspherical lens 30 corresponds to a point where the optical axes of the multiple collimated beams 20b converge. However, in reality, the positions of the multiple collimated beams 20b are shifted, and the beam diameters of the multiple collimated beams 20b are different, so that all the collimated beams 20b do not necessarily converge to one point. In addition, even if there is no shift in position and the beam diameters are the same, there is a diffraction limit of light for the width at which all the collimated beams 20b can be converged, so it may be considered that all the collimated beams 20b do not converge to the point shown in the figure. In this specification, for convenience of explanation, the light-converging point F is simplified to one point.

[0034] As shown in FIG. 3A and FIG. 3B, the light incident surface 40s1 of the light-transmitting region 40t is orthogonal to the optical axis of the aspherical lens 30 and is positioned away from the light-converging point F of the aspherical lens 30. The distance between the light incident surface 40s1 of the light-transmitting region 40t and the light-converging 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 irradiated with the converged multiple collimated beams 20b without changing the traveling direction of the collimated beams 20b by a reflecting mirror or the like. In the example shown in FIG. 3A and FIG. 3B, the light-converging 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 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 aspheric 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 irradiated with a plurality of defocused collimated beams 20b. This makes it possible to reduce the light density of the collimated beams 20b on the light incident surface 40s1, compared to when the light incident surface 40s1 of the light-transmitting region 40t coincides with the focal point F of the aspherical lens 30.

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

number

[0037] z represents the distance in the Z direction between the XY plane including 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 aspheric lens 30. 2i (2i=2, . . . , n) represents the aspheric 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 when = 0, equation (1) represents any of the following curved surfaces: hyperboloid, paraboloid, sphere, or ellipsoid.

[0040] Next, refer to FIG. 4. FIG. 4 is a graph plotting the curved surface of the lens shown in Equation (1) when a 2i = 0. The conic constant was 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 curved surface of the graph is as follows. The curved 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 curved 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 curved surface of the lens of the aspherical lens 30 corresponds to the curved 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 curved surface other than the conic constant k = 0.

[0041] Next, with reference 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 irradiated collimated beam converged by the convex portion 30c with a conic constant k = +0.5. In 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 axis in the X direction is 1.0 mm, and the major axis 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) or more. The center interval of two adjacent collimated beams 20b in the row direction (X direction) is 3.5 mm, and the center interval 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 curvature radius 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. The distance from the flat portion 30f of the aspherical lens 30 to the focal point F in the case of k=+0.5 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 distribution of the four irradiated collimated beams at the ends in the row direction (X direction) is shaped to extend toward the four corners of the light incident surface 40s1 of the rectangular light-transmitting region 40t. In this way, the multiple collimated beams 20b have at least a pair of outer collimated beams irradiated to 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 the aspherical lens 30 reduces the concentration of the irradiated collimated beam 20b. In other words, the aspherical lens 30 has a shape that causes the outer collimated beam to diverge more than the inner collimated beam. As described above, the proportion of fluorescence increases at the end portions of the light-transmitting region 40t, especially at the four corners, due to reflection at the reflection region 40r. When the intensity distribution of the irradiated collimated beam is dispersed to the end portion, particularly the four corners, of the light incident surface 40s1 of the light-transmitting region 40t, the proportion of the collimated beam 20b at that portion is increased compared to the case where the intensity distribution is not dispersed. As a result, the color of the light emitted at the end portion, 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 can reduce the color unevenness of 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 to a degree of divergence in which the beam width of the outer collimated beam is 1.1 times or more the beam width of the inner collimated beam in the beam width in the divergence direction, and preferably 1.3 times or more. This can further reduce color unevenness. In addition, since the optical density of the outer collimated beam decreases as the outer collimated beam diverges, it is preferable that the degree of divergence is such that the beam width of the outer collimated beam is 2.5 times or less than the beam width of the inner collimated beam. The beam width in the diverging 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 to be compared in 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, with reference to FIG. 6, the relationship between the conic constant k of the lens and the intensity distribution of the irradiation collimated beam will be described. FIG. 6 is a diagram showing the calculation results of the intensity distribution of a 2-row 5-column irradiation 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 irradiation 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 in the range of -15 < k < 0 or 0 < k < +6.

[0044] In the above-described example, 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 typical methods for modulating the intensity distribution of the irradiation 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] The light source 20 is configured to mount a plurality of semiconductor light-emitting elements 25 in one package, so that the light-emitting device 100 can be made smaller. This is because the shortest distance between the collimated beams 20b emitted from two adjacent semiconductor light-emitting elements 25 in one package is easier to make smaller than the shortest distance between the collimated beams 20b emitted from two adjacent packages when the light source 20 is configured in a plurality of packages. In other words, by mounting a plurality of semiconductor light-emitting elements 25 in one package, the irradiation range of the plurality of collimated beams 20b can be made smaller than the case where the same number of semiconductor light-emitting elements 25 are divided and arranged in a plurality of packages. This allows the size of the aspherical lens 30 to be reduced, and the light-emitting device 100 to be made smaller.

[0047] The desired state of the intensity distribution of the irradiated collimated beam can be determined according to the shape of the light incident surface 40s1 of the light-transmitting region 40t. Therefore, the aspheric shape of the surface of the convex portion 30c of the aspheric 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 shape of the light incident surface 40s1 of the light-transmitting region 40t is a circular, elliptical, or oval shape, the color unevenness of the mixed light may be reduced by the aspheric lens 30 having the convex portion 30c whose conic constant is negative (k<0). The oval shape means a shape similar to a circular or elliptical shape, a closed curve that does not intersect, and a shape that is line-symmetric at at least one point. When the collimated beams 20b are arranged in a matrix, it can be said from the results shown in FIG. 6 that the four corners of the matrix-shaped collimated beams 20b tend to shrink toward the center as the conic constant is negative (k<0) and the absolute value is increased. In addition, it can be said that the greater the absolute value of the conic constant is, the more the four corners of the matrix-like collimated beam 20b tend to spread 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 aspheric 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 aspheric 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 the light source 20 will be described with reference to Fig. 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. For convenience of explanation, the base 21 and the optical element 24 are depicted as being farther apart than they actually are.

[0050] The semiconductor light emitting elements 25 are arranged in two rows and five columns on the main surface 21s of the base 21 via the submount 26. The emission end faces of the semiconductor light emitting elements 25 arranged in one row face the emission end faces of the semiconductor light emitting elements 25 arranged in the other row. In this way, the semiconductor light emitting elements 25 are arranged in a matrix of one row or more and two columns or two rows or more and one column or more along a plane (XY plane) perpendicular to the optical axis of the aspheric 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 can reduce the influence of heat generated by the semiconductor light emitting elements 25. On the other hand, in consideration of miniaturization of the light source 20, it is desirable that the center-to-center distance between adjacent semiconductor light emitting elements 25 is, 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] The light reflecting members 27 are arranged in two rows and five columns on the main surface 21s of the base 21. The 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 the light emitted from the semiconductor light emitting element 25. The angle between the reflecting surface 27r of the light reflecting member 27 and the main surface 21s of the base 21 is determined by the arrangement relationship of the semiconductor light emitting element 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. The 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 semiconductor light emitting elements 25 arranged in two rows, 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), metal such as aluminum, or Si. The reflecting surface 27r of the light reflecting member 27 is desirably formed of a material having a relatively high reflectance to 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 at the peak wavelength of the light emitted by the semiconductor light emitting element 25, and may be 90%. The light reflecting member 27 may have a plurality of light reflecting surfaces. The light source 20 may further include a light reflecting member other than the light reflecting member 27.

[0053] The optical element 24 includes collimator lenses 24l arranged in 2 rows and 5 columns. The collimator lenses 24l are provided at positions where the light emitted from the semiconductor light emitting element 25 passes through the collimator lenses 24l. The optical element 24 emits 2-row and 5-column collimated beams from the collimator 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 direction and the Y direction 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 the semiconductor light emitting elements 25 may be more than one. To reduce the size of the light source 20, the number may be, for example, 30 or less. The same applies to the collimator 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. The 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 electrode may be formed of a light-transmitting conductive material and used as a cladding layer. A voltage is applied to the n-side electrode and the p-side electrode to pass a current equal to or greater than a threshold value, and the laser diode emits a laser beam. In FIG. 7A, the laser beam is emitted in a direction parallel to the Y direction from the end face of the semiconductor light emitting element 25. The spot of the emitted laser beam has an elliptical shape with the Z direction as the long axis and the X direction as the far field pattern. The laser diode can emit laser beam of any color in the visible range, for example. When light outside the visible range is utilized as part of the mixed light, the laser diode may emit laser beam 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 has 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, more preferably in the range of 440 nm to 460 nm. As a laser diode that emits blue laser light, a semiconductor laser element containing a nitride semiconductor can be used. As the nitride semiconductor, for example, GaN, InGaN, and AlGaN can be used. The semiconductor laser element containing a nitride semiconductor can emit light from the ultraviolet to the visible region by changing the composition.

[0058] The semiconductor light emitting element 25 may be hermetically sealed by a package as necessary. The base 21, the frame 22, and the lid 23 correspond to 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 (for example, a wavelength of about 480 nm or less), if the emission end face of the laser diode is in contact with the outside air, there is a possibility that end face deterioration will progress during operation due to a dust collection effect, etc. Such end face deterioration may lead to a decrease in the optical output of the laser diode. In order to increase the reliability of the laser diode and extend its life, it is desirable to hermetically seal the laser diode.

[0059] The semiconductor light emitting element 25 may include a light emitting diode (LED) that emits incoherent light. Since laser light can reduce light loss when combined with a lens, 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 desirably made of a material with a relatively high thermal conductivity in order to quickly release heat generated from the semiconductor light emitting elements 25 to the outside. Similarly, the submount 26 is desirably made of a material with a 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, silicon carbide, etc.

[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 provided with a metal film via a conductive layer such as Au-Sn. The semiconductor light emitting element 25 may be provided so as to directly emit light in the Z direction. In this case, the light reflecting member 27 is not necessary. In the area of ​​the submount 26 other than the area where the semiconductor light emitting elements 25 are provided, a conductive layer for wire connection may be provided to facilitate electrical connection between the multiple semiconductor light emitting elements 25 and the lead terminals 22l on the frame 22 by wires.

[0062] Next, with reference to FIG. 7B and FIG. 7C, the difference in beam width of the collimated beam 20b shown in FIG. 3A and FIG. 3B will be described. Here, the semiconductor light emitting element 25 includes a laser diode. FIG. 7B and FIG. 7C are cross-sectional views in the YZ plane and the XZ plane, respectively, which show a state in which 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 cover body 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 spreads widely in the Z direction and does not spread so much in the X direction. Therefore, as shown in FIG. 7B, when the laser light that spreads widely in the Z direction is reflected upward and collimated, the beam width of the collimated beam 20b in the Y direction becomes wider. In contrast, as shown in Fig. 7C, when a laser beam that does not expand much in the X direction is reflected upward and collimated, the beam width of the collimated beam 20b in the X direction does not expand much. Therefore, the spot of the collimated beam 20b emitted in the Z direction from the 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 the laser beam emitted from the semiconductor light-emitting element 25 is not limited to the shape described here, and may have, for example, the major and minor axes reversed.

[0063] (Modification of light collecting part having aspheric surface) Next, a modified example of the light collecting section having an aspheric surface in the present disclosure will be described with reference to Figs. 8A and 8B. Figs. 8A and 8B are side views seen from the Y direction, which show a state in which the collimated beam 20b emitted from the light source 20 is converged by the parabolic reflector 31 in the modified example and is incident on the light incident surface 40s1 of the light transmitting region 40t in the wavelength conversion section 40. In Figs. 8A and 8B, the substrate 10 and the housing 50 are omitted. The parabolic reflector 31 in the modified example has a reflecting surface 31m having a parabolic shape. The reflecting surface 31m reflects light traveling parallel to the axis 31a (Z direction) of the parabolic surface and causes it to converge to a focusing point F on the axis 31a. It is not necessary that all parts of the reflecting surface 31m shown in Figs. 8A and 8B are present, and only the parts on which light hits are required. There is no restriction on the shape of the parts of the parabolic reflector 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 among 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 central beam is reflected in the X direction by the reflecting surface 31m. 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 away 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 to the focusing point F. The central beam is reflected in an obliquely upward direction by the reflecting surface 31m. The mixed light is emitted in an obliquely upward direction from the light emitting surface 40s2 of the wavelength conversion 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 in an obliquely downward direction from the light emitting surface 40s2 of the wavelength conversion unit 40.

[0065] 8A and 8B, the light-concentration 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 aspheric lens 30 and the light-concentration point F. The light-concentration point F may 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 aspheric shape such as a hyperbolic or ellipsoidal shape depending on the application. Even if the light collecting part having an aspheric surface in the present disclosure is an aspheric reflecting mirror such as the parabolic reflecting mirror 31, the color unevenness of the mixed light can be reduced. [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 Base main surface 22 Frame 22l Lead terminal on the frame 23 Lid 24 Optical Elements Collimating lenses in 24l optical elements 25 Semiconductor light emitting device 26 Submount 27 Light reflecting material 27r Reflective surface of light-reflecting member 30 Aspheric Lenses 30c Convex 30f flat plate part 31 Parabolic reflector 31a Paraboloid axis 31m reflective surface 40 Wavelength conversion section 40r reflective area 40s1 Light incidence surface 40s2 Light exit surface 40t transparent area 50 Case 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 light emitted from each of the plurality of semiconductor light emitting elements to output a plurality of collimated beams; a parabolic or aspheric shaped reflecting surface for reflecting the collimated beams to thereby converge the collimated beams; a light-transmitting region having a light incident surface located between the reflecting surface and a light-focusing point at which light reflected by the reflecting surface converges, or on the opposite side of the reflecting surface across the light-focusing point; Equipped with Light emitting device.

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

3. The plurality of semiconductor light emitting elements are arranged in a matrix of one row or more and two columns or two rows or more and one column or more.

3. The light emitting device according to claim 1 or 2.

4. The shape of the light incident surface of the light-transmitting region is rectangular. The light emitting device according to claim 1 .

5. The plurality of semiconductor light emitting elements are a plurality of laser diodes. A light emitting device according to claim 1 .

6. a package for hermetically sealing the plurality of laser diodes; The light emitting device according to claim 5 .

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