JP6067629B2 - Light emitting device, lighting device, and vehicle headlamp - Google Patents

Description

  The present invention relates to a light-emitting device, a lighting device, and a vehicle headlamp that use fluorescence generated by irradiating phosphor with excitation light.

  In recent years, semiconductor light emitting devices such as light emitting diodes (LEDs) and semiconductor lasers (LDs) are used as excitation light sources, and excitation light generated from these excitation light sources is emitted to light emitting units including phosphors. Research on light-emitting devices that use fluorescence generated by the above as illumination light has become active.

  An example of such a light emitting device is a vehicular lamp disclosed in Patent Document 1. In this vehicle lamp, an LED module or an LD module is used as an excitation light source, and white light is generated by irradiating excitation light onto a small spot-like phosphor having a diameter of about 0.5 mm or less.

Japanese Unexamined Patent Publication No. 2004-241142 (released on August 26, 2004)

  The objective of this invention is providing the light-emitting device which can control easily the magnitude | size of the spot of the excitation light irradiated to a light emission part.

  The conversion efficiency of the phosphor is about 90% at the maximum, and the excitation light that has not been converted to fluorescence becomes heat. Therefore, as the excitation density increases, the temperature of the phosphor increases, and the conversion efficiency of the phosphor. Decreases.

  In particular, when excitation is performed with Gaussian beam-shaped excitation light (for example, laser light), a region in which the peak (top) portion of the beam is irradiated and a region in which the bottom portion of the beam is irradiated are generated. There is a problem that the conversion efficiency in the region irradiated with the portion is lowered, and the total conversion efficiency is lowered. Such a problem cannot be solved by the invention of Patent Document 1.

In order to solve the above-described problem, a light-emitting device according to the present invention transmits the excitation light emitted from the excitation light source and has a first optical member having an emission surface that emits the excitation light; A light emitting portion that emits fluorescence upon receiving the excitation light emitted from the emission surface; and a second optical member positioned between the emission surface and the light emission portion, and the light from the emission surface and the light emission portion. The spot of the excitation light on the irradiation surface has an optical conjugate relationship, and the distribution shape of the excitation light on the emission surface is the same as the distribution shape of the excitation light on the light emitting portion.

  According to the light emitting device of the present invention, there is an effect that the size of the spot of the excitation light irradiated to the light emitting unit can be easily controlled.

It is the schematic which shows the structure of the laser element which concerns on one Embodiment of this invention. It is a figure which shows the type of spatial light intensity distribution of excitation light. It is sectional drawing which shows schematic structure of the headlamp which concerns on one Embodiment of this invention. It is a figure which shows an example of the shape of the laser beam spot in the laser beam irradiation surface of a light emission part. (A) And (b) is a figure which shows another example of the shape of the laser beam spot in the laser beam irradiation surface of a light emission part. It is the schematic which shows the structure of the laser element which concerns on another embodiment of this invention. It is the schematic which shows the structure of the laser element which concerns on another embodiment of this invention. It is the schematic which shows the structure of the laser element which concerns on another embodiment of this invention. It is the schematic which shows the structure of the laser element which concerns on another embodiment of this invention.

[Embodiment 1]
One embodiment of the present invention will be described below with reference to FIGS.

<Technical idea of the present invention>
First, the technical idea of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing the type of spatial light intensity distribution of excitation light.

  In the condensing optical system, the condensing spot size is determined by the divergence angle of the excitation light source and the size of the excitation light source. Therefore, the size of the excitation light source is important in the condensing optical system.

  When a semiconductor laser is used as an excitation light source, the spatial intensity distribution of laser light emitted from the semiconductor laser usually has a Gaussian distribution (leftmost beam shape in FIG. 2). In the Gaussian distribution, the energy intensity differs between a region irradiated with the peak (top) portion of the beam and a region irradiated with the bottom portion of the beam.

  On the other hand, there is a top hat distribution as another spatial intensity distribution (center beam shape in FIG. 2). The top hat distribution is a distribution in which the energy intensity distribution of the excitation light on the surface irradiated with the excitation light is substantially flat.

  In the case of the same light quantity and the same beam width, in the Gaussian distribution, the light intensity in the region irradiated with the peak portion of the excitation light may be five times higher than the light intensity in the top hat distribution.

  Since the excitation light that has not been converted to fluorescence becomes heat, the temperature of the phosphor increases as the excitation density increases. If the temperature of the phosphor increases, the conversion efficiency of the phosphor decreases by quenching the temperature. Therefore, when the excitation light having a Gaussian distribution is irradiated, the conversion efficiency in the region irradiated with the peak portion is lowered, and the total conversion efficiency may be lowered. As a result, there is a possibility that the total fluorescent light flux obtained may be reduced (darkened) as compared with the case where the top hat distribution excitation light is irradiated.

  In order to solve this problem, the present invention prevents the phosphor conversion efficiency from being lowered by the heat of the excitation light by using the top hat-shaped beam as the excitation light that irradiates the light emitting part including the phosphor. To do.

  In addition, since the gauss beam shape has a skirt, the contrast between the excited part and the non-excited part is poor, optical design is difficult, and the skirt part cannot be used optically. is there.

  This problem can also be solved by irradiating excitation light having a top hat distribution.

  When the Gaussian distribution type peak intensity is the same as that of the top hat distribution type and the comparison is made with the same beam width (the rightmost beam shape in FIG. 2), the radiated light flux is reduced to 60%. In this case, the excitation light emitted from a portion larger than the necessary light source size becomes stray light in the condensing optical system and forms an unintended image. Therefore, an extra optical component such as a slit for blocking stray light is required. Therefore, it is preferable to irradiate the excitation light having a top hat distribution.

<Configuration of headlamp 1>
Here, a headlamp (vehicle headlamp) 1 that satisfies the light distribution characteristic standard of a traveling headlamp (high beam) for automobiles will be described as an example of the light emitting device or lighting device of the present invention. However, the lighting device of the present invention may be a headlight for passing (low beam), and is realized as a headlamp of a vehicle other than an automobile or a moving object (for example, a human, a ship, an aircraft, a submersible, a rocket). Or may be realized as another lighting device. Examples of other lighting devices include a searchlight, a projector, a home lighting device, a commercial lighting device, and an outdoor lighting device.

  FIG. 3 is a cross-sectional view showing a schematic configuration of a headlamp (vehicle headlamp) 1 according to an embodiment of the present invention. As shown in FIG. 3, the headlamp 1 includes a laser element (excitation light source) 2, a lens (second optical member) 3, a light emitting unit 4, a parabolic mirror (light projecting member, reflector) 5, a metal base 7, and fins 8. It has.

  The headlamp 1 generates fluorescence by irradiating the light emitting unit 4 with excitation light from the laser element 2, and uses the fluorescence as illumination light. In this headlamp 1, the energy intensity distribution of the excitation light irradiated to the light emitting unit 4 is a top hat distribution.

(Laser element 2)
The laser element 2 is a light emitting element that functions as an excitation light source that emits excitation light, and is, for example, a semiconductor laser. If strictly interpreted, it can be said that the laser chip 21 (see FIG. 1) included in the laser element 2 is an excitation light source. The laser element 2 includes an optical rod 23 (first optical member) that converts the energy intensity distribution of laser light into a top hat distribution by multiple reflection inside. Details of the configuration of the laser element 2 will be described later.

  A plurality of laser elements 2 may be provided. In this case, laser light as excitation light is oscillated from each of the plurality of laser elements 2. Although only one laser element 2 may be used, it is easier to use a plurality of laser elements 2 in order to obtain a high-power laser beam.

  Further, the laser element 2 may have one light emitting point on one chip, or may have a plurality of light emitting points on one chip. The wavelength of the laser light of the laser element 2 is, for example, 405 nm (blue purple) or 450 nm (blue), but is not limited thereto, and may be appropriately selected according to the type of phosphor included in the light emitting unit 4. .

  An LED may be used as an excitation light source for the headlamp 1. However, since the semiconductor laser has better coupling efficiency with respect to the optical rod 23 than the LED, it is preferable to use the semiconductor laser as an excitation light source.

(Lens 3)
The lens 3 is a second optical member that irradiates the light emitting unit 4 with the laser light emitted from the optical rod 23 of the laser element 2 and controls the size of the spot of the laser light to irradiate the light emitting unit 4. To do.

  By providing the lens 3, the emission surface 23 b of the optical rod 23 and the spot of the excitation light irradiated on the light emitting unit 4 can be in an optical conjugate relationship, and the spot of the excitation light irradiated on the light emitting unit 4. It becomes easy to control the size of the.

  By changing the design of the curved surface of the lens 3 or changing the distance between the lens 3 and the light emitting unit 4, the size of the laser light spot on the laser light irradiation surface 4 a of the light emitting unit 4 can be changed. .

  This lens 3 is, for example, a convex lens. The lens 3 is disposed for each of the laser elements 2, and the positional relationship between the lens 3 and the laser element 2 is such that the emission surface 23 b of the optical rod 23 is positioned at one focal position of the lens 3. It is prescribed. The positional relationship between the lens 3 and the light emitting unit 4 is defined so that the laser light irradiation surface 4a of the light emitting unit 4 is positioned at the other focal position of the lens 3.

  As will be described later, the laser light emitted from the optical rod 23 has a top hat-shaped spatial light intensity distribution, and the lens 3 irradiates the light emitting unit 4 with the laser light.

  A concave mirror or the like may be used as the second optical member provided in the headlamp 1 in place of the lens 3, and the second optical member is not particularly limited as long as it can control the size of the laser light spot.

(Light emitting part 4)
The light emitting unit 4 emits fluorescence upon receiving the laser light emitted from the laser element 2, and includes a phosphor (fluorescent substance) that emits light upon receiving the laser light. Specifically, the light emitting unit 4 is one in which a phosphor is dispersed inside a sealing material, or a phosphor is solidified. The light emitting unit 4 can be said to be a wavelength conversion element because it converts laser light into fluorescence.

  The light emitting unit 4 is disposed on the metal base 7 and at a substantially focal position of the parabolic mirror 5. Therefore, the fluorescence emitted from the light emitting unit 4 is reflected on the reflection curved surface of the parabolic mirror 5 so that the optical path is controlled. An antireflection structure for preventing the reflection of the laser beam may be formed on the laser beam irradiation surface 4 a of the light emitting unit 4.

Examples of the phosphor of the light emitting unit 4 include an oxynitride phosphor (for example, a sialon phosphor), a nitride phosphor (for example, a CASN (CaAlSiN ₃ ) phosphor), or a group III-V compound semiconductor nanoparticle phosphor (for example). For example, indium (InP) can be used. However, the phosphor of the light emitting unit 4 is not limited to the above-described phosphor, and may be other phosphors.

  Further, it is stipulated by laws and regulations that the illumination light of the headlamp must be white having a predetermined range of chromaticity. Therefore, the light emitting unit 4 includes a phosphor selected so that the illumination light has a predetermined white color.

  For example, when blue, green, and red phosphors are included in the light emitting unit 4 and irradiated with laser light of 405 nm, white light is generated. Alternatively, a yellow phosphor (or green and red phosphor) is included in the light-emitting portion 4, and a so-called blue laser having a peak wavelength in a wavelength range of 450 nm (blue) to 450 nm (blue) or 440 nm to 490 nm. White light can also be obtained by irradiating light.

  The sealing material of the light emitting unit 4 is, for example, a resin material such as a glass material (inorganic glass or organic-inorganic hybrid glass) or a silicone resin. Low melting glass may be used as the glass material. The sealing material is preferably highly transparent, and when the laser beam has a high output, a material having high heat resistance is preferable.

(Parabolic mirror 5)
The parabolic mirror 5 is an example of a light projecting member that reflects the fluorescence generated by the light emitting unit 4 and forms a light bundle (illumination light) that travels within a predetermined solid angle. The parabolic mirror 5 may be, for example, a member having a metal thin film formed on the surface thereof or a metal member.

  The parabolic mirror 5 is at least a part of a partial curved surface obtained by cutting a curved surface (parabolic curved surface) formed by rotating the parabola about the axis of symmetry of the parabola with a plane including the rotational axis. Is included in the reflective surface.

  The laser element 2 is disposed outside the parabolic mirror 5, and the parabolic mirror 5 is formed with a window portion 6 that transmits or passes the laser light. The window 6 may be an opening or may include a transparent member that can transmit laser light. For example, a transparent plate provided with a filter that transmits laser light and reflects white light (fluorescence of the light emitting section 4) may be provided as the window section 6. In this configuration, the fluorescence of the light emitting unit 4 can be prevented from leaking from the window unit 6.

  One common window portion 6 may be provided for the plurality of laser elements 2, or a plurality of window portions 6 corresponding to the respective laser elements 2 may be provided.

  A part that is not a parabola may be included in a part of the parabola mirror 5. In addition, the reflecting mirror (reflector) included in the light emitting device of the present invention may include a parabolic mirror having a closed circular opening or a part thereof. The reflecting mirror is not limited to a parabolic mirror, and may be an elliptical mirror, a free-form surface mirror, or a multi-mirror.

  In addition, a lens may be used as a light projecting member that projects illumination light including fluorescence obtained from the light emitting unit 4 in a desired direction. This lens is an optical system that projects fluorescence in a predetermined light projecting direction by transmitting and refracting the fluorescence.

  The light emission 4 parts excited by laser light having a top hat-shaped energy intensity distribution emit fluorescence having a top hat-shaped energy intensity distribution. When such fluorescent light is projected by the above-described light projecting member (for example, parabolic mirror 5), almost all of the fluorescent luminous flux emitted from the light emitting unit 4 can be used, and a highly efficient light projecting system. Can be realized.

(Metal base 7)
The metal base 7 is a plate-like support member that supports the light emitting unit 4 and is made of metal (for example, aluminum or copper). Therefore, the metal base 7 has high thermal conductivity, and can efficiently dissipate heat generated by the light emitting unit 4.

  In addition, the member which supports the light emission part 4 is not limited to what consists of metals, The member containing substances (silicon carbide, aluminum nitride, etc.) with high heat conductivity other than a metal may be sufficient. However, it is preferable that the surface of the metal base 7 in contact with the light emitting unit 4 functions as a reflecting surface. Since the surface is a reflection surface, after the laser light incident from the laser light irradiation surface 4a of the light emitting unit 4 is converted into fluorescence, the generated fluorescence is reflected by the reflection surface and directed to the parabolic mirror 5. Can do. Alternatively, the laser light incident from the laser light irradiation surface 4 a of the light emitting unit 4 can be reflected by the reflection surface and again converted into fluorescence by going toward the inside of the light emitting unit 4.

(Fin 8)
The fin 8 functions as a cooling unit (heat dissipation mechanism) that cools the metal base 7. The fin 8 has a plurality of heat radiating plates, and increases the heat radiation efficiency by increasing the contact area with the atmosphere. The cooling unit that cools the metal base 7 may have a cooling (heat radiation) function, and may be a heat pipe, a water cooling method, or an air cooling method.

<Details of Laser Element 2>
FIG. 1 is a schematic diagram showing a configuration of a laser element 2 according to this embodiment. As shown in FIG. 1, the laser element 2 includes a laser chip (excitation light source) 21, a submount 22, an optical rod 23, an AR (Anti Reflection) coating film 24, a cap 25, a stem 26, and lead terminals 27. .

(Laser chip 21 etc.)
The laser chip 21 is a chip-shaped semiconductor laser element that emits laser light as excitation light. The configuration of the laser chip 21 (for example, the material of the semiconductor layer) is not particularly limited. The laser chip 21 is fixed to the submount 22, and the submount 22 is fixed to the stem 26.

  The submount 22 functions as a heat sink for exhausting heat generated when the laser chip 21 is driven. Therefore, aluminum nitride and SiC, which are materials having high thermal conductivity, can be used.

  As a material constituting the stem 26, gold-plated iron, gold-plated copper, or the like can be used. From the viewpoint of exhausting heat generated in the laser chip 21, the stem 26 is also preferably made of a metal having high thermal conductivity.

  A lead terminal 27 is connected to the laser chip 21 through a fine gold wire (not shown), and power is supplied from an external power source through these wires.

(Optical rod 23)
The optical rod 23 is an optical member (first optical member) that converts the energy intensity distribution of the laser light emitted from the laser chip 21 into a top hat distribution. The optical rod 23 includes an incident surface 23a that receives laser light and an output surface 23b that emits laser light. The incident surface 23 a is formed at one end of the optical rod 23, and the exit surface 23 b is formed at the other end of the optical rod 23.

  The incident surface 23 a is disposed in the vicinity of the light emitting point of the laser chip 21, and the laser light emitted from the light emitting point enters the optical rod 23 from the incident surface 23 a.

  The laser light emitted from the light emitting point is light having a Gaussian distribution-shaped spatial light intensity distribution, but a top-hat-shaped spatial light intensity distribution is generated by a plurality of reflections while passing through the inside of the optical rod 23. Converted into light.

  The emission end portion on which the emission surface 23 b is formed extends through the cap 25 to the outside of the laser element 2, and the emission surface 23 b is disposed at one focal position of the lens 3. Therefore, the laser light emitted from the emission surface 23 b is efficiently irradiated onto the laser light irradiation surface 4 a of the light emitting unit 4 by the lens 3.

  An AR coating film (antireflection structure) 24, which is an antireflection film, is disposed on the incident surface 23a. Therefore, it is possible to prevent the laser light from being reflected on the incident surface 23a, and to reduce the loss when the laser light is incident on the inside of the optical rod 23. The AR coating film 24 may be provided on the emission surface 23b. The AR coating film 24 is an example of an antireflection structure, and other antireflection structures including a moth-eye structure may be provided on the incident surface 23a.

  Note that it is not always necessary to extend the emission end portion on which the emission surface 23b is formed to the outside of the laser element 2. The emission surface 23b is housed inside the cap 25, and the laser beam emitted from the emission surface 23b is transmitted. Cap glass (window) may be provided on the cap 25. Whether or not the emission end portion on which the emission surface 23b is formed is extended to the outside of the laser element 2 depends on the length of the optical rod 23 necessary for converting the laser light into light having a top hat-shaped spatial light intensity distribution. Depends on the size.

  In the example shown in FIG. 1, the length of the optical rod 23 is 20 mm, and the rod diameter is 0.4 mm. However, the size of the optical rod 23 is not limited to this.

  FIG. 4 is a diagram illustrating an example of the shape of the laser beam spot 41 on the laser beam irradiation surface 4 a of the light emitting unit 4. The optical rod 23 is, for example, a square pole, and the emission surface 23b is a square (for example, a rectangle or a square). The shape of the laser beam spot 41 reflects the shape of the emission surface 23b. Therefore, the shape of the laser beam spot 41 can be changed to a desired shape by changing the shape of the emission surface 23b.

  When the plurality of optical rods 23 or laser beam spots 41 are arranged adjacent to each other by making the shape of the emission surface 23b of the optical rod 23 polygonal, the gaps between the optical rods 23 or between the laser beam spots. Can be reduced. As a result, the irradiation density of laser light can be increased and efficient irradiation can be performed.

  FIGS. 5A and 5B are diagrams showing another example of the shape of the laser beam spot 41 on the laser beam irradiation surface 4a of the light emitting unit 4. FIG. As shown in FIG. 5A, the shape of the emission surface 23b may be defined so that the laser light spot 41 is a more complex polygon. Further, as shown in FIG. 5B, the laser light spot 41 may have a shape including a curved portion and a corner portion.

  The illumination light emitted from the headlamp 1 forms an illumination light spot having a shape corresponding to the shape of the laser light spot 41 in the light emitting unit 4.

  A laser beam spot 41 shown in FIGS. 5A and 5B has a shape corresponding to the light distribution characteristic of a low-pass headlight. By making the shape of the laser light spot 41 (in other words, the shape of the emission surface 23b) such a shape, a light distribution pattern corresponding to the light distribution characteristics of the low-pass headlight can be realized.

  That is, the optical rod 23 has an emission surface 23b for emitting laser light, and the shape of the emission surface 23b corresponds to a desired light distribution pattern. This technical idea can also be applied to the first optical member 29 and the multimode fiber 31 described later.

  Conventionally, in order to realize a specific light distribution pattern, a part of the illumination light is blocked by a mask (light shielding plate) or a mirror cut. However, in this configuration, a loss of illumination light occurs. By making the shape of the emission surface 23b a shape corresponding to the desired light distribution characteristic, the desired light distribution characteristic can be realized without causing a loss of illumination light.

(Cap 25)
The cap 25 is a member for enclosing or sealing a member such as the laser chip 21. In particular, the relative position between the laser chip 21 and the optical rod 23 is fixed by the cap 25. The inside of the cap 25 may be hollow, and may be filled with a material such as resin or low-melting glass. Moreover, you may form the whole cap 25 with low melting glass.

<Effect of headlamp 1>
In the headlamp 1, the laser element 2 is provided with an optical rod 23 that converts the spatial energy intensity distribution of the laser light emitted from the laser chip 21 into a top hat shape. Then, the top hat-shaped laser beam is irradiated onto the laser beam irradiation surface 4 a of the light emitting unit 4 through the lens 3.

  Therefore, the laser beam is irradiated onto the laser beam irradiation surface 4a with a substantially uniform light intensity. As a result, it is possible to prevent the conversion efficiency of the phosphor from being lowered at the location where the temperature of a part of the laser light irradiation surface 4a is locally increased by the laser light.

  In addition, in the spatial light intensity distribution having a Gaussian distribution shape, the irradiation range continuously expands from a region where the laser light irradiation intensity is high to a low region on the laser light irradiation surface 4a, so that the portion excited by the laser light is excited. The contrast with the unexposed part is lowered. On the other hand, by irradiating the laser light irradiation surface 4a of the light emitting unit 4 with laser light having a top hat-shaped spatial light intensity distribution, the contrast between the portion excited by the laser light and the portion not excited is increased. The optical design of the headlamp 1 can be facilitated, and the light beam can be effectively used.

  Further, the light emitting units can be classified into two types based on the relationship between the irradiation direction of the laser light to the light emitting unit 4 and the emission direction of the fluorescence emitted from the light emitting unit 4.

  In the present application, a light-emitting part of a type in which laser light emitted from the laser element 2 is irradiated onto the laser light irradiation surface 4a of the light-emitting part 4 and fluorescence is emitted mainly on the side opposite to the laser light irradiation surface 4a is referred to as “transmission type”. Will be referred to as a “light emitting portion”. In the configuration including the transmissive light emitting unit, for example, the light emitting unit 4 is disposed on a substrate having an opening, and the laser element 2 is positioned after the laser light applied to the light emitting unit 4 is converted into fluorescence. The fluorescence is emitted mainly on the side opposite to the side.

  In the transmissive light emitting unit, the laser light is scattered inside the light emitting unit 4 to expand the spatial light intensity distribution. Therefore, it may not always be necessary to provide an optical member for realizing a top hat-shaped spatial light intensity distribution. However, in this case as well, the spatial light intensity distribution having a Gaussian distribution shape is maintained, and the top hat-shaped spatial light intensity distribution is not realized.

  On the other hand, a light emitting part of a type in which laser light emitted from the laser element 2 is irradiated onto the light emitting part 4 and fluorescence is emitted mainly on the side where the laser element 2 is located is referred to as a reflective light emitting part in the present application. To. In the reflective light emitting unit 4 shown in FIG. 3, the region having the strongest intensity in the distribution of fluorescence emitted from the light emitting unit 4 is divided into two by the plane including the surface on which the light emitting unit 4 is placed (the surface of the metal base 7). Among the spaces, the laser light irradiation surface 4a of the light emitting unit 4 that receives the laser light is included in the space. By forming a gap between the optical rod 23, which is the first optical member, and the light emitting unit 4, a reflective light emitting unit can be realized.

  In the reflection type light emitting part, it is assumed that a part of the laser light is transmitted through the light emitting part 4, but also in this case, the fluorescence is mainly emitted to the side where the laser element 2 is located. The case will be referred to as a reflective light emitting unit.

  As described above, in the transmissive light emitting unit, it is assumed that the spatial light intensity distribution is expanded by scattering the laser light. Therefore, it is considered that the technical significance of the light emitting device of the present invention is enhanced by being realized as a light emitting device having a reflective light emitting unit. However, the present invention may be applied to a light-emitting device having a transmissive light-emitting portion for the purpose of realizing a top hat-shaped spatial light intensity distribution.

  In the transmissive light emitting unit, the laser beam diffuses while the laser beam is transmitted through the light emitting unit 4, and thus it may be difficult to form the laser beam spot 41 having a desired shape. Therefore, when the shape of the emission surface 23b is made to correspond to a desired light distribution characteristic, it is preferable to realize the present invention as a light emitting device having a reflective light emitting unit rather than a transmissive type.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to FIG. In addition, about the member similar to Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the present embodiment, the headlamp 1 includes a laser element 20 instead of the laser element 2. Other configurations are the same as those in the first embodiment.

<Configuration of Laser Element 20>
FIG. 6 is a schematic diagram showing a configuration of another laser element 20 applicable to the headlamp 1. In the laser element 20, an aluminum coat 28 is applied to the side surface of the optical rod 23.

  Therefore, it is possible to prevent the laser light from leaking from the side surface of the optical rod 23 while the laser light is transmitted through the optical rod 23.

  In addition, the film | membrane applied to the side surface of the optical rod 23 is not limited to an aluminum coat, The reflection film which consists of a material with another high reflectance may be sufficient.

[Embodiment 3]
The following will describe another embodiment of the present invention with reference to FIG. Note that members similar to those in the first and second embodiments are given the same reference numerals, and descriptions thereof are omitted.

  In the present embodiment, the headlamp 1 includes a laser element 40 instead of the laser element 2. Other configurations are the same as those in the first and second embodiments.

<Configuration of Laser Element 40>
FIG. 7 is a schematic diagram showing a configuration of another laser element 40 applicable to the headlamp 1. The laser element 40 includes a first optical member 29 instead of the optical rod 23. The first optical member 29 in the present embodiment is a hollow member having a plurality of inner surfaces 29c that are reflecting surfaces.

  The material and structure of the first optical member 29 in this embodiment are not particularly limited. For example, a hollow prism (for example, a quadrangular prism) is formed by a plurality of mirror surfaces.

  The length of the first optical member 29 is, for example, 20 mm, and one side of the emission end portion 29b is, for example, 0.4 mm. However, the length of the first optical member 29 and the size of the cross section are as follows. It is not limited to.

  Laser light is incident from an incident end portion 29 a which is one end portion of the first optical member 29. The incident laser light advances while being reflected on the inner surface 29c of the first optical member 29, and is emitted from the emission end portion 29b which is the other end portion.

  The laser beam emitted from the emission end portion 29 b is controlled by the lens 3. By providing the lens 3, the emission end portion 29b of the first optical member 29 and the spot of the excitation light irradiated on the light emitting portion 4 are in an optical conjugate relationship, and the laser light emitted from the emission end portion 29b. Is efficiently irradiated onto the laser light irradiation surface 4 a of the light emitting unit 4 by the lens 3. Further, by providing the lens 3, it becomes easy to control the size of the spot of the excitation light irradiated on the light emitting unit 4.

  The laser light emitted from the light emitting point of the laser chip 21 is light having a spatial light intensity distribution having a Gaussian distribution shape. By repeating reflection inside the first optical member 29, the spatial light intensity distribution having a top hat shape is obtained. Converted to light.

  The emission end portion 29 b is located inside the cap 25, and the laser light emitted from the emission end portion 29 b passes through the cap glass 30 provided on the cap 25 and is emitted to the outside of the laser element 2.

  An AR coating film 24 a is disposed between the emission end portion 29 b and the cap glass 30. By providing the AR coating film 24a, it is possible to prevent the emission efficiency from being lowered by the reflection of the laser light on the surface of the cap glass 30 to the inside of the first optical member 29.

<Effect of Laser Element 40>
In the laser element 40, the laser light emitted from the laser chip 21 is passed through the first optical member 29, whereby the spatial light intensity distribution of the laser light can be converted into a top hat distribution.

  As a result, the laser beam can be irradiated onto the laser beam irradiation surface 4a with a substantially uniform light intensity, and the phosphor conversion efficiency can be prevented from being reduced by the heat of the laser beam.

  In addition, since the laser light can be transmitted from the first optical member 29 with almost no leakage, the energy efficiency can be increased.

  In addition, since the tolerance of optical coupling between the first optical member 29 and the laser is very large, there is an advantage that strict alignment is not required and that the first optical member 29 is resistant to vibration.

[Embodiment 4]
The following will describe another embodiment of the present invention with reference to FIG. In addition, about the member similar to Embodiment 1-3, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the present embodiment, the headlamp 1 includes a laser element 50 instead of the laser element 2. Other configurations are the same as those in the first to third embodiments.

<Configuration of Laser Element 50>
FIG. 8 is a schematic diagram showing a configuration of another laser element 50 applicable to the headlamp 1. The laser element 50 includes a multimode fiber (first optical member) 31 instead of the optical rod 23. The multimode fiber 31 is an optical fiber having a plurality of modes of light propagating in the optical fiber, and has a two-layer structure in which the core of the core is covered with a clad having a refractive index lower than that of the core. The core is mainly composed of, for example, quartz glass (silicon oxide) that has almost no absorption loss of laser light, and the cladding is composed mainly of, for example, quartz glass or a synthetic resin material having a refractive index lower than that of the core. To do.

  The length of the multimode fiber 31 is, for example, 20 mm, and the diameter thereof is, for example, 0.4 mm. However, the length and thickness of the multimode fiber 31 are not limited to this.

  Laser light is incident from an incident surface 31a located at one end of the multimode fiber 31, and the incident laser light advances while being reflected inside the core of the multimode fiber 31, and is located at the other end. The light exits from the exit surface 31b.

  Laser light emitted from the emission surface 31 b is controlled by the lens 3. By providing the lens 3, the emission surface 31b of the multimode fiber 31 and the spot of the excitation light irradiated on the light emitting unit 4 can be in an optical conjugate relationship, and the laser light emitted from the emission surface 31b can be efficiently used. The laser light irradiation surface 4a of the light emitting unit 4 can be irradiated well. Further, by providing the lens 3, it becomes easy to control the size of the spot of the excitation light irradiated on the light emitting unit 4.

  The laser light emitted from the light emitting point of the laser chip 21 is light having a spatial light intensity distribution having a Gaussian distribution shape. By repeating reflection inside the core of the multimode fiber 31, the spatial light intensity distribution having a top hat shape is obtained. Converted into light.

  Similar to the laser element 2, the AR coating film 24 may be provided on the incident surface 31 a of the multimode fiber 31.

<Effect of laser element 50>
In the laser element 50, by passing the laser light emitted from the laser chip 21 through the multimode fiber 31, the spatial light intensity distribution of the laser light can be converted into a top hat distribution.

  As a result, the laser beam can be irradiated onto the laser beam irradiation surface 4a with a substantially uniform light intensity, and the phosphor conversion efficiency can be prevented from being reduced by the heat of the laser beam.

  Further, when the multimode fiber 31 is used, a long optical member (for example, 1 to 5 m) is formed as compared with the case where the optical rod 23 or the first optical member 29 is used (usually about 10 to 20 mm is selected). Easy to do. In the case of a long optical member, the number of reflections of the laser beam inside the optical member increases, so that the intensity distribution is made uniform and a top hat type spatial light intensity distribution with a more uniform distribution can be realized. In addition, there is an advantage that the degree of freedom of arrangement of the laser elements can be increased.

[Embodiment 5]
The following will describe another embodiment of the present invention with reference to FIG. In addition, about the member similar to Embodiment 1-4, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the present embodiment, the headlamp 1 includes a laser element 60 instead of the laser element 2. Other configurations are the same as those in the first to fourth embodiments.

<Configuration of Laser Element 60>
FIG. 9 is a schematic diagram showing a configuration of another laser element 60 applicable to the headlamp 1. The laser element 60 includes a first lens (first optical member) 32 and a second lens (first optical member) 33 instead of the optical rod 23.

  The first lens 32 condenses the laser light emitted from the laser chip 21 onto the principal point of the second lens 33, and the second lens 33 converts the laser light condensed by the first lens 32 to the light emitting unit 4. Irradiate the laser light irradiation surface 4a. That is, with respect to the first lens 32, the emission end face of the laser chip 21 and the second lens 33 have a conjugate relationship, and with respect to the second lens, the first lens 32 and the light emitting unit 4 have a conjugate relationship. It is assumed to be an arrangement.

  The first lens 32 is fixed to the cap 25 by a fixing part 34 made of low-melting glass, and the second lens 33 is fixed to the cap 25 by a fixing part 35 made of low-melting glass. However, the fixing method of the 1st lens 32 and the 2nd lens 33 is not limited to this method, What kind of thing may be sufficient.

  The first lens 32 and the second lens 33 may be a set of convex lenses.

  The number of lenses sealed in the laser element 60 is not limited to two and may be three or more.

  Further, the second lens 33 may be outside the laser element 60. That is, some of the plurality of lenses constituting the first optical member may be disposed inside the laser element 60, and the remaining lenses may be disposed outside the laser element 60.

  In the configuration in which the first lens 32 and the second lens 33 are provided, the lens 3 is not necessarily provided. Whether to provide the lens 3 may be determined based on the lens characteristics and arrangement of the first lens 32 and the second lens 33.

  Further, the second lens 33 may be the same size as the first lens 32 or may be larger than the first lens 32.

<Effect of Laser Element 60>
In the laser element 60, the spatial light intensity distribution of the laser light emitted from the laser chip 21 can be converted into a top hat-shaped distribution by the first lens 32 and the second lens 33.

  As a result, the laser beam can be irradiated onto the laser beam irradiation surface 4a with a substantially uniform light intensity, and the phosphor conversion efficiency can be prevented from being reduced by the heat of the laser beam. Further, by using the first lens 32 and the second lens 33 as the first optical member, the laser element and the headlamp 1 can be realized at a lower cost than when the optical rod 23 or the like is used.

(Additional notes)
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  For example, a top-hat type laser beam distribution may be created using a fly-eye lens. A fly-eye lens is a lens in which a plurality of lenses (biconvex lenses or semi-convex lenses) are arranged in a matrix.

  The present invention can also be expressed as follows.

  That is, the light-emitting device according to the present invention includes a light-emitting unit that emits fluorescence upon receiving excitation light emitted from an excitation light source, and the excitation light source is a laser light source, and has the highest intensity in the distribution of fluorescence emitted by the light-emitting unit. The strong region is included in the space where the surface of the light emitting unit that receives the excitation light is located in the space divided into two by the plane including the surface on which the light emitting unit is placed. The energy intensity distribution of the irradiated excitation light is a top hat distribution.

  In the light emitting device according to the present invention, only a part of the surface of the light emitting unit irradiated with the excitation light is irradiated with the excitation light.

  The light emitting device according to the present invention further includes a first optical member that converts the energy intensity distribution of the excitation light into a top hat distribution.

  In the light emitting device according to the present invention, there is a gap between the first optical member and the light emitting unit.

  In addition, the light emitting device according to the present invention further includes a light projecting member that projects illumination light including fluorescence obtained from the light emitting unit in a desired direction.

  In the light emitting device according to the present invention, the light projecting member is a reflector.

  The light emitting device according to the present invention further includes a second optical member that irradiates the light emitting unit with excitation light emitted from the first optical member while controlling a size of the spot of the excitation light. .

  In the light emitting device according to the present invention, the first optical member has an exit surface that emits excitation light, and the exit surface has a polygonal shape.

  In the light emitting device according to the present invention, the first optical member has an emission surface that emits excitation light, and the shape of the emission surface corresponds to a desired light distribution pattern.

  In the light emitting device according to the present invention, the first optical member includes a multimode fiber, a hollow member having an inner surface which is a reflecting surface, or an optical rod.

  In the light emitting device according to the present invention, the first optical member includes first and second lenses, and the excitation light source and the second lens are in a conjugate relationship with respect to the first lens, Regarding the lens, the first lens and the light emitting portion are in a conjugate relationship.

  In the light emitting device according to the present invention, the first optical member has an incident surface for receiving the excitation light, and the incident surface is provided with an antireflection structure.

  The vehicle headlamp according to the present invention includes the light emitting device according to the present invention.

  In the vehicle headlamp according to the present invention, the light emitting device further includes a first optical member that converts an energy intensity distribution of the excitation light into a top hat distribution, and the first optical member emits excitation light. The shape of the emission surface corresponds to the light distribution pattern of the passing lamp in the vehicle headlamp.

  The lighting device according to the present invention includes the light emitting device according to the present invention.

  Furthermore, the present invention can be expressed as follows.

  That is, in order to solve the above-described problem, the light-emitting device according to the present invention includes a light-emitting unit that emits fluorescence in response to excitation light emitted from an excitation light source, and energy intensity of excitation light irradiated on the light-emitting unit. The distribution is characterized by a top-hat distribution.

  According to said structure, the energy intensity distribution of the excitation light irradiated to a light emission part is a top hat distribution. The top hat distribution is a distribution in which the energy intensity distribution is substantially flat. Therefore, it is possible to prevent the light emitting portion from being excited locally by excitation light with high energy intensity, and the possibility of temperature quenching due to local high temperature can be reduced. As a result, the conversion efficiency of excitation light into fluorescence can be increased.

  Further, the contrast between the excited portion and the non-excited portion can be increased, and the optical design can be facilitated.

  The light emitting device preferably further includes a first optical member that converts the energy intensity distribution of the excitation light into a top hat distribution.

  With the above configuration, when the energy intensity distribution of the excitation light emitted from the excitation light source is, for example, a Gaussian distribution, the energy intensity distribution can be converted into a top hat distribution by the first optical member.

  Moreover, it is preferable that there is a gap between the first optical member and the light emitting unit.

  With the above configuration, when the excitation light emitted from the first optical member is applied to the light emitting unit, fluorescence can be emitted to the same side as the incident side of the excitation light. It is possible to realize a “light emitting unit”.

  Moreover, it is preferable that the said light-emitting device is further provided with the light projection member which projects the illumination light containing the fluorescence obtained from the said light emission part in a desired direction.

  The light projecting member may be a reflector.

  With the above configuration, illumination light including fluorescence obtained from the light emitting unit can be projected in a desired direction. In addition, the light emitting portion excited by the excitation light having the top hat-shaped energy intensity distribution emits fluorescence having the top hat-shaped energy intensity distribution. When such fluorescent light is projected by the light projecting member, almost all of the fluorescent luminous flux emitted from the light emitting unit can be used, and a highly efficient light projecting system can be realized.

  In addition, when the light emitting part is excited with excitation light having a Gaussian distribution, the part of the light emitting part that is excited at the part corresponding to the tail of the Gaussian distribution in the excitation light may emit a sufficient amount of fluorescence. The fluorescence generated by the portion corresponding to the skirt cannot be used effectively as stray light.

  The light emitting device preferably further includes a second optical member that irradiates the light emitting unit with the excitation light emitted from the first optical member while controlling the size of the spot of the excitation light. .

  With the above configuration, the size of the spot of the excitation light irradiated on the light emitting unit can be controlled, and the irradiation range of the illumination light can be changed.

  The first optical member preferably has an exit surface that emits excitation light, and the exit surface is preferably polygonal.

  According to said structure, since the shape of the output surface of an optical member is a polygon (for example, quadrangle | tetragon), when arrange | positioning a several optical member or the spot of excitation light adjacent to each other, between optical members or excitation The gap between the light spots can be reduced.

  Moreover, it is preferable that the said 1st optical member has the output surface which radiate | emits excitation light, and the shape of the said output surface respond | corresponds to a desired light distribution pattern.

  According to said structure, the light distribution pattern of illumination light can be made into a desired thing by making the shape of the said output surface correspond to a desired light distribution pattern.

  The first optical member may include a multimode fiber, a hollow member having an inner surface that is a reflection surface, or an optical rod.

  With the above configuration, when the energy intensity distribution of the excitation light emitted from the excitation light source is, for example, a Gaussian distribution, the energy intensity distribution can be converted into a top hat distribution by the first optical member.

  The first optical member includes a first lens and a second lens. The excitation light source and the second lens are in a conjugate relationship with respect to the first lens, and the first lens with respect to the second lens. And the light emitting portion are preferably in a conjugate relationship.

  With the above configuration, it becomes easy to control the size of the spot of the excitation light irradiated on the light emitting unit.

  The first optical member preferably has an incident surface that receives the excitation light, and the incident surface is preferably provided with an antireflection structure.

  According to said structure, since the antireflection structure (for example, antireflection film (AR coat)) is provided in the incident surface of the optical member, reflection of the excitation light in an incident surface can be prevented. As a result, loss when the excitation light is incident on the optical member can be reduced.

  The region with the strongest intensity in the distribution of fluorescence emitted by the light emitting unit is the surface of the light emitting unit that receives the excitation light in a space divided by a plane including the surface on which the light emitting unit is placed. It is preferable that it is contained in the located space.

  According to said structure, fluorescence is radiate | emitted to the same side as the incident side of excitation light (this structure is called a "reflective light emission part" in this application). In a configuration in which fluorescence is emitted mainly on the side opposite to the surface of the light emitting portion irradiated with the excitation light (this configuration is referred to as a “transmissive light emitting portion” in the present application), the excitation light passes through the light emitting portion. However, this is not the case with a reflective light emitting part. Therefore, it is particularly useful to use the optical member in a reflective light emitting unit.

  Further, a vehicle headlamp including the light emitting device and a lighting device including the light emitting device are also included in the technical scope of the present invention.

  The light emitting device further includes a first optical member that converts the energy intensity distribution of the excitation light into a top hat distribution, and the first optical member has an emission surface that emits the excitation light. The shape of the surface preferably corresponds to the light distribution pattern of the passing lamp in the vehicular headlamp.

  With the above configuration, the light distribution pattern of the vehicular headlamp can be adapted to the light distribution pattern of the passing light that is legally defined.

  As described above, the light-emitting device according to the present invention includes a light-emitting unit that emits fluorescence in response to excitation light emitted from an excitation light source, and the energy intensity distribution of the excitation light irradiated to the light-emitting unit is a top-hat distribution. It is the composition which is.

  Therefore, the light-emitting portion is not locally excited by excitation light with high energy intensity, and the possibility that the temperature can be quenched by locally becoming high temperature can be reduced.

  The present invention can be applied to light-emitting devices and lighting devices, particularly headlamps for vehicles.

1 Headlamp 2 Laser element (excitation light source)
3 Lens (second optical member)
4 Light emitting unit 20 Laser element (excitation light source)
21 Laser chip (excitation light source)
23 Optical rod (first optical member)
23a Incident surface 23b Emission surface 24 AR coat film (antireflection structure)
29 first optical member 29a incident end 29b exit end 29c inner surface 24a AR coat film (antireflection film)
31 Multimode fiber (first optical member)
31a Incident surface 31b Outgoing surface 32 First lens (first optical member)
33 Second lens (first optical member)
40 Laser element (excitation light source)
41 Laser light spot 50 Laser element (excitation light source)
60 Laser element (excitation light source)

Claims (9)

A first optical member that transmits the excitation light emitted from the excitation light source and has an emission surface that emits the excitation light; and
A light emitting unit that emits fluorescence in response to the excitation light emitted from the emission surface;
A second optical member positioned between the emission surface and the light emitting unit,
The exit surface and the spot of the excitation light on the light irradiation surface of the light emitting unit are in an optical conjugate relationship,
The light-emitting device, wherein a distribution shape of the excitation light on the emission surface is the same as a distribution shape of the excitation light on the light-emitting portion.   The light emitting device according to claim 1, wherein the first optical member is an optical fiber having one exit surface.   3. The light emitting device according to claim 1, wherein a spatial light intensity distribution of excitation light on the emission surface of the first optical member has a top hat shape.   4. The light-emitting device according to claim 1, wherein the first optical member has a structure in which a plurality of reflections are generated when the excitation light is transmitted through the first optical member. 5.   5. The light-emitting device according to claim 1, wherein a region where the excitation light is transmitted on the emission surface has at least one linear edge.   The light emitting device according to claim 1, wherein the emission surface has a planar shape.   The light emitting device according to any one of claims 1 to 6, wherein the first optical member is a multimode fiber or an optical rod.   An illumination device comprising the light-emitting device according to claim 1. A vehicular headlamp comprising the lighting device according to claim 8.

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