JP2011129375A - Headlamp for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To design a headlamp smaller than a conventional one. <P>SOLUTION: The headlamp 1 includes a semiconductor laser 3 to emit laser beams, a light emitting part 7 which receives laser beams emitted from the semiconductor laser 3 and emits light, and a reflecting mirror 8 which reflects light emitted from the light emitting part 7. In the headlamp 1, the luminous flux irradiated from the light emitting part 7 is larger than 600 lm, and the luminance of the light emitting part 7 is stronger than 75 cd/mm<SP>2</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle headlamp that can be designed to be smaller than a conventional lamp, and more particularly to a traveling headlamp.

  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 a technique related to such a light emitting device is a lamp disclosed in Patent Document 1. In this lamp, a semiconductor laser is used as an excitation light source in order to realize a high-intensity light source. Since the laser light oscillated from the semiconductor laser is coherent light, the directivity is strong, and the laser light can be condensed and used as excitation light without waste. A light-emitting device using such a semiconductor laser as an excitation light source (referred to as an LD light-emitting device) can be suitably applied to a vehicle headlamp.

  In addition, there is a lamp disclosed in Patent Document 2 as an example of a technique in which the wavelength conversion material emits visible light by irradiating the wavelength conversion material with infrared light. In this lamp, a wavelength conversion material is provided at the focal position of the concave mirror, and the function as a light source is exhibited by reflecting visible light emitted from the wavelength conversion material by the concave mirror. The configuration in which the wavelength conversion material is provided at the focal position of the concave mirror of Patent Document 2 is applied to the installation of the parabolic reflection surface or the elliptical reflection surface and the phosphor in the lamp of Patent Document 1.

Moreover, there exists a lamp disclosed in patent document 3 as an example of the technique regarding the said light-emitting device. A light emitting device having a good color rendering property is realized by using a yellow phosphor in addition to blue, green and red phosphors in the light emitting portion of the lamp. Note that the lamp of Patent Document 3 can emit light having a luminous flux, luminance, and color rendering properties similar to those of a halogen lamp with a luminous flux of about 1200 lumens (lm) and a luminance of about 25 cd / mm ² .

  An example of a technique for realizing a vehicle headlamp using an incoherent white LED is a vehicle headlamp disclosed in Non-Patent Document 1.

JP 2005-150041 A (released on June 9, 2005) Japanese Patent Laid-Open No. 7-318998 (released on December 8, 1995) JP 2007-294754 A (published November 8, 2007)

Masaru Sasaki, “Application of White LED to Automotive Lighting”, Journal of Applied Physics, 2005, Vol. 74, No. 11, p. 1463-1466

  However, Patent Document 1 does not disclose how much laser light is output and how much incoherent light is emitted when the light emitting unit is irradiated. For this reason, it is unclear to what extent the size of the optical system (the concave mirror and the lens provided on the concave mirror) can be reduced in order to realize a lamp that emits light of a constant luminous intensity.

  Here, the constant luminous intensity refers to, for example, the luminous intensity of the highest luminous intensity point in a high beam for vehicles stipulated in Japanese domestic law, and currently, 29500 to 112500 cd (candela) per lamp, It is stipulated that the sum of the maximum luminous intensity of the lamps (2 or 4) per minute does not exceed 225000 cd.

  That is, in Patent Document 1, for example, regarding miniaturization in consideration of practical use of a lamp, such as a durability problem that a light emitting part deteriorates severely when a minute light emitting part including a phosphor is excited with high power excitation light. Is not touched at all.

Further, Patent Document 3 does not mention the realization of a lamp having a luminance greater than 25 cd / mm ² . For this reason, in patent document 3, it can be said that it is not assumed that size reduction of a lamp is achieved by implement | achieving a high-intensity lamp. In addition, the lamp of patent document 3 is invention regarding the fluorescent substance used for a light emission part, and aims at the improvement of luminous efficiency and color rendering property. Further, the present inventors have found that the most important factor in reducing the size of the lamp is to increase the luminance.

  The present invention has been made to solve the above problems, and an object thereof is to provide a vehicle headlamp that can be designed to be smaller than a conventional lamp.

In order to solve the above problems, a vehicle headlamp according to the present invention includes an excitation light source that emits excitation light, a light emitting unit that emits light by receiving excitation light emitted from the excitation light source, and the light emitting unit. And a reflecting mirror that reflects the light emitted from the light emitting portion, the luminous flux emitted from the light emitting portion is larger than 600 lm, and the luminance of the light emitting portion is larger than 75 cd / mm ² .

For example, when a conventional halogen lamp is used as a headlight for traveling, the luminance of the halogen lamp is 20 to 25 cd / mm ² , so that light that satisfies the minimum value of light intensity defined by domestic laws is emitted. In this case, it is necessary to keep the opening surface of the reflecting mirror (more precisely, the opening surface of the reflecting mirror perpendicular to the traveling direction of the light emitted to the outside of the device) at a certain area or more. In other words, in the conventional halogen lamp, the “certain area” is a factor that hinders downsizing of the apparatus.

In this regard, the vehicular headlamp according to the present invention has a luminance of the light emitting unit greater than 75 cd / mm ^2, so that even if the area of the opening surface of the reflecting mirror is significantly smaller than the above-mentioned “certain area”, Light that satisfies the prescribed luminous intensity range can be emitted. And since the light beam radiated | emitted from a light emission part is larger than 600lm, sufficient brightness is ensured. That is, the vehicle headlamp according to the present invention has a luminous flux radiated from the light emitting portion larger than 600 lm and the luminance of the light emitting portion larger than 75 cd / mm ^2, so that it is compared with a conventional lamp (vehicle headlamp). And miniaturization can be achieved.

An example of a conventional lamp is an HID (High Intensity Discharge) lamp having a luminance of 75 cd / mm ² . However, the HID lamp has a problem that the instantaneous lighting performance is not excellent, and it is known that the HID lamp is not suitable for a vehicle headlamp (for example, a traveling headlamp) that requires instantaneous lighting performance.

  Furthermore, the vehicle headlamp according to the present invention can be expected to have a special effect as compared with a conventional lamp in terms of weight reduction and power saving.

  Specifically, the vehicle headlamp according to the present invention can achieve a reduction in size as compared with a conventional lamp. Accordingly, it is possible to reduce the weight of the device itself with the downsizing of the device. Therefore, when the vehicle headlamp according to the present invention is used as a traveling headlamp for a vehicle, for example, Fuel consumption can be improved.

  Furthermore, the vehicle headlamp according to the present invention achieves higher luminance and higher luminous flux than conventional lamps. Therefore, if it is going to implement | achieve the brightness | luminance and luminous flux comparable as the conventional lamp, what is necessary is just to reduce the power consumption of an excitation light source, and can achieve power saving by the part which reduced the power consumption.

  As described above, the vehicle headlamp according to the present invention can simultaneously realize the weight reduction and power saving of the apparatus. Therefore, against the background of the recent increase in environmental awareness, the vehicle headlamp according to the present invention. Can be applied to a vehicle headlight very suitably.

  As described above, the vehicular headlamp according to the present invention can realize a lighting device that is downsized compared to a conventional lamp, and further improves fuel consumption and reduces power consumption by reducing the weight of the device. Can also be realized.

  The vehicle headlamp according to the present invention includes a light guide unit having an incident end that receives excitation light emitted from the excitation light source, and an emission end that emits excitation light incident from the incident end to the light emitting unit. It is preferable to provide.

  According to the above configuration, the vehicle headlamp according to the present invention includes the light guide unit that guides the excitation light emitted from the excitation light source to the light emitting unit between the excitation light source and the light emitting unit. It can be installed away from the light emitting part. For this reason, the design freedom degree of the vehicle headlamp can be increased, for example, the excitation light source can be installed at a position where it is easy to cool or replace.

  In the vehicle headlamp according to the present invention, it is preferable that the excitation light source emits excitation light having a peak wavelength in a wavelength range of 400 nm to 420 nm.

  According to the above configuration, since the excitation light source emits excitation light of 400 nm or more and 420 nm or less, that is, blue-violet or near-color excitation light, the light emitting part material (phosphor material) for generating white light is used. Easy to select and manufacture. That is, a vehicle headlamp that can easily generate white light can be realized.

  In the vehicle headlamp according to the present invention, it is preferable that the excitation light source emits excitation light having a peak wavelength in a wavelength range of 440 nm to 490 nm.

  According to the above configuration, the excitation light source emits excitation light of 440 nm or more and 490 nm or less, that is, blue or near-color excitation light, so that it is easy to use a light emitting part material (phosphor material) for generating white light. Can be selected and manufactured. That is, a vehicle headlamp that can easily generate white light can be realized.

  The vehicle headlamp according to the present invention is preferably a vehicle headlamp.

For example, when a conventional halogen lamp is used as a traveling headlamp, if the area of the opening surface is smaller than 2000 mm ² , there is a possibility that light having the minimum value in the above-mentioned luminous intensity range cannot be emitted. In addition, since conventional HID lamps are not excellent in instantaneous lighting performance, they are not suitable for traveling headlamps that require instantaneous lighting performance.

  Therefore, the vehicle headlamp of the present invention can be realized as a traveling headlamp that is smaller than a conventional lamp in consideration of practicality.

As described above, the headlamp for an illuminated vehicle according to the present invention, the excitation light source that emits the excitation light, the light emitting unit that emits light by receiving the excitation light emitted from the excitation light source, and the light emission unit emitted A light-reflecting mirror that reflects light, and the luminous flux emitted from the light-emitting portion is larger than 600 lm, and the luminance of the light-emitting portion is larger than 75 cd / mm ² .

  Therefore, there is an effect that it is possible to realize a vehicular headlamp that is smaller than a conventional lamp.

It is a figure which shows schematic structure of the headlamp which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the headlamp as a modification which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the headlamp as another modified example which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the brightness | luminance of the headlamp for vehicles (automobile) using each light source, and the optical system area of the said headlamp. (A) is a figure which shows the circuit diagram of a semiconductor laser typically, (b) is a perspective view which shows the basic structure of a semiconductor laser. It is sectional drawing which shows the structure of the headlamp which concerns on another form of this invention. It is a figure which shows the positional relationship of the output end part and light emission part of an optical fiber with which the headlamp which concerns on another form of this invention is provided. It is sectional drawing which shows the example of a change of the positioning method of a light emission part. (A) is a figure which shows the light distribution characteristic requested | required of the headlight for passing for motor vehicles, (b) is a figure which shows the illumination intensity prescribed | regulated to the light distribution characteristic standard of the headlight for passing. .

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS. Here, as an example of the present invention, 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. However, the vehicle headlamp according to the present invention is a vehicle / moving object other than an automobile (for example, human / It may be realized as a headlamp of a ship, an aircraft, a submarine, a rocket, etc.

(Configuration of headlamp 1)
First, the configuration of the headlamp 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration of a headlamp 1 according to the present embodiment. The headlamp 1 is an example of a configuration for realizing a headlamp that is smaller than a conventional headlamp.

  As shown in the figure, the headlamp 1 includes a semiconductor laser (excitation light source) 3, an aspherical lens 4, a truncated pyramid shaped optical member (light guide part) 21, a light emitting part 7, a reflecting mirror 8, and a transparent plate 9. ing. The basic structure of the light emitting device is formed by the semiconductor laser 3, the truncated pyramidal optical member 21, and the light emitting unit 7.

  The headlamp 1 includes a housing 10, an extension 11, and a lens 12 as in the headlamp 1a according to the second embodiment, but is not shown in FIG. In this embodiment, the truncated pyramid-shaped optical member 21 will be described as an example. However, the shape of the optical member is not limited to this, and various shapes such as a truncated cone shape and an elliptical truncated cone shape can be employed. A specific configuration in the case where the optical member has a truncated cone shape will be described later as a modified example of the headlamp 1.

  The semiconductor laser 3 functions as an excitation light source that emits excitation light, and may be formed on a substrate to form a semiconductor laser array. Laser light (excitation light) is oscillated from each of the semiconductor lasers 3.

  The semiconductor laser 3 has six light emitting points (six stripes) in one chip. For example, the semiconductor laser 3 oscillates a laser beam having a wavelength of 405 nm (blue purple) and has an output of 4.0 W, an operating voltage of 5 V, and a current of 2.67 A. It is enclosed in a 9 mm diameter package. The laser beam oscillated by the semiconductor laser 3 is not limited to 405 nm, and may be a laser beam having a peak wavelength in a wavelength range of 380 nm to 470 nm. The wavelength may be 400 nm or more and 420 nm or less. In this case, the headlamp 1 can easily select and manufacture the material (phosphor material) of the light emitting unit 7 for generating white light. If a high-quality semiconductor laser for a short wavelength that oscillates a laser beam having a wavelength smaller than 380 nm can be manufactured, the laser beam having a wavelength smaller than 380 nm is oscillated as the semiconductor laser 3 of this embodiment. It is also possible to use a semiconductor laser designed for the above.

  As shown in FIG. 1, since the three semiconductor lasers 3 are mounted, the output of the semiconductor laser 3 as a whole is 12 W, and the power consumption is 40 W (= 5 V × 2.67 A × 3). It is not always necessary to use a plurality of semiconductor lasers 3 as the excitation light source, and only one semiconductor laser 3 may be used. However, in order to obtain a high-power laser beam, it is preferable to use a plurality of semiconductor lasers 3.

  The aspherical lens 4 is a lens for causing laser light (excitation light) oscillated from each semiconductor laser 3 to enter the light incident surface 211 that is one end of the truncated pyramidal optical member 21. For example, as the aspheric lens 4, FLKN1 405 manufactured by Alps Electric can be used. The shape and material of the aspherical lens 4 are not particularly limited as long as the lens has the above function, but it is preferably a material having a high transmittance near 405 nm and a good heat resistance.

  The truncated pyramidal optical member 21 is a light guide member that condenses the laser light oscillated by the semiconductor laser 3 and guides it to the light emitting portion 7 (laser light irradiation surface 7 a of the light emitting portion 7). And is optically coupled to the semiconductor laser 3. The truncated pyramid-shaped optical member 21 includes a light incident surface 211 (incident end portion) that receives the laser light emitted from the semiconductor laser 3 and a light emitting surface 212 (emits the laser light incident from the light incident surface 211 to the light emitting portion 7. Output end).

  Thereby, since the semiconductor laser 3 and the light emitting unit 7 sandwich the truncated pyramidal optical member 21, the semiconductor laser 3 can be set apart from the light emitting unit 7. For this reason, the design freedom of the headlamp 1 can be increased, for example, the semiconductor laser 3 can be installed at a position where it is easy to cool or replace.

  When the bottom (excitation light incident end 211) of the truncated pyramidal optical member 21 and the semiconductor laser 3 can be installed sufficiently close, the aspheric lens 4 may not be provided. By adopting such a configuration, the structure is further simplified, and since one element that attenuates the excitation light is eliminated, the efficiency can be further improved.

  Coupling efficiency of the aspherical lens 4 and the truncated pyramid shaped optical member 21 (laser light emitted from the light emitting surface 212 of the truncated pyramid shaped optical member 21 when the intensity of the laser light emitted from the semiconductor laser 3 is 1) Strength) is 90%. For this reason, when the 12 W laser light emitted from the semiconductor laser 3 passes through the aspherical lens 4 and the truncated pyramidal optical member 21, it is emitted from the light emitting surface 212 as 10.8 W laser light.

  The truncated pyramidal optical member 21 has a surrounding structure surrounded by a truncated pyramid side surface (light reflecting side surface, surrounding structure) 213 that reflects each laser beam incident from the light incident surface 211, and a light emitting surface 212. Is smaller than the cross-sectional area of the light incident surface 211. The truncated pyramid shaped optical member 21 guides each laser beam incident from the light incident surface 211 to the light emitting surface 212 through the truncated pyramid side surface 213. The truncated pyramidal optical member 21 is made of BK7, quartz glass, acrylic resin, or other transparent material. Further, the light incident surface 211 may have a planar shape or a curved surface shape.

  Thus, each laser beam incident from the light incident surface 211 is guided to the light emitting surface 212 having a smaller cross-sectional area than the light incident surface 211 by the truncated pyramid side surface 213, that is, each laser beam is The light can be condensed on the light exit surface 212.

  In addition, a light emitting surface 212 is formed at the other end of the truncated pyramid side surface 213 so that each of the guided laser beams is distributed and irradiated on the laser light irradiation surface 7 a of the light emitting unit 7. The light exit surface 212 has a structure in which a plano-convex cylindrical lens having an axis in the vertical direction is integrated with the light exit surface 212.

  In the present embodiment, the light emitting surface 212 and the cylindrical lens are integrated (that is, the light emitting surface 212 has a curved shape). However, the present invention is not limited to this, and the light emitting surface 212 may be provided separately. Good. In this case, the cylindrical lens is provided between the light emitting surface 212 and the light emitting unit 7. Further, the light exit surface 212 in this case may be a planar shape or a curved surface shape. In the case of a curved surface shape, the light emitting surface 212 is not limited to a convex lens shape, and is a concave lens shape or a combination of a convex lens and a concave lens. Also good. The lens shape may be spherical, aspherical, cylindrical, or the like. Further, in some cases, the light emitting unit 7 may be closely attached and installed with a flat light emitting surface.

  In addition, each laser beam is reflected only once on the truncated pyramid side surface 213 and guided to the light emitting surface 212, or is reflected on the truncated pyramid side surface 213 a plurality of times and guided to the light emitting surface 212. The light is guided by any one of the optical paths in the case of being guided to the light emitting surface 212 without being reflected once on the side surface 213 of the truncated pyramid.

  The light emitting unit 7 emits light by receiving the laser light emitted from the light emitting surface 212, and includes a phosphor that emits light by receiving the laser light. Specifically, the light emitting unit 7 is a phosphor in which a phosphor is dispersed inside a silicone resin as a phosphor holding substance. The ratio of silicone resin to phosphor is about 10: 1. In addition, the light emitting unit 7 may be formed by pressing a fluorescent material. The phosphor holding substance is not limited to silicone resin, and may be so-called organic-inorganic hybrid glass or inorganic glass.

  The phosphor is of an oxynitride type, and blue, green and red phosphors are dispersed in a silicone resin. Since the semiconductor laser 3 oscillates 405 nm (blue-violet) laser light, white light is generated when the light emitting unit 7 is irradiated with the laser light. Therefore, it can be said that the light emitting portion 7 is a wavelength conversion material.

  The semiconductor laser 3 may oscillate a 450 nm (blue) laser beam (or a so-called “blue” laser beam having a peak wavelength in a wavelength range of 440 nm to 490 nm). The phosphor is a yellow phosphor or a mixture of a green phosphor and a red phosphor. In other words, the semiconductor laser 3 may emit excitation light having a peak wavelength in the wavelength range of 440 nm or more and 490 nm or less. In this case, the light emitting part material (phosphor material) for generating white light is used. Easy to select and manufacture. The yellow phosphor is a phosphor that emits light having a peak wavelength in a wavelength range of 560 nm to 590 nm. The green phosphor is a phosphor that emits light having a peak wavelength in a wavelength range of 510 nm or more and 560 nm or less. The red phosphor is a phosphor that emits light having a peak wavelength in a wavelength range of 600 nm to 680 nm.

The phosphor is preferably a so-called sialon phosphor. Sialon is a substance in which a part of silicon atoms in silicon nitride is replaced with aluminum atoms and a part of nitrogen atoms is replaced with oxygen atoms. The sialon phosphor can be produced by dissolving alumina (Al ₂ O ₃ ), silica (SiO ₂ ), a rare earth element, and the like in silicon nitride (Si ₃ N ₄ ).

  As another suitable example of the phosphor, a semiconductor nanoparticle phosphor using nanometer-sized particles of a III-V compound semiconductor can be exemplified.

  One of the features of semiconductor nanoparticle phosphors is that even if the same compound semiconductor (for example, indium phosphorus: InP) is used, the emission color is changed by the quantum size effect by changing the particle diameter to nanometer size. It is a point that can be. For example, InP emits red light when the particle size is about 3 to 4 nm (here, the particle size was evaluated with a transmission electron microscope (TEM)).

  In addition, since this semiconductor nanoparticle phosphor is semiconductor-based, it has a short fluorescence lifetime and can emit the excitation light power as fluorescence quickly, so that it is highly resistant to high-power excitation light. This is because the emission lifetime of the semiconductor nanoparticle phosphor is about 10 nanoseconds, which is five orders of magnitude smaller than that of a normal phosphor material having a rare earth as the emission center.

  Furthermore, as described above, since the emission lifetime is short, the absorption of the laser beam and the emission of the phosphor can be quickly repeated. As a result, high efficiency can be maintained with respect to strong laser light, and heat generation from the phosphor can be reduced.

  Therefore, it is possible to further suppress the deterioration (discoloration or deformation) of the light emitting unit 7 due to heat. Thereby, when using the light emitting element with a high light output as a light source, it can suppress more that the lifetime of a light-emitting device (it mentions later about a basic structure) becomes short.

The shape and size of the light emitting unit 7 are, for example, a rectangular parallelepiped of 3 mm × 1 mm × 1 mm. In this case, the area of the laser light irradiation surface 7a that receives the laser light from the semiconductor laser 3 (the light receiving surface of the light emitting portion 7 facing the light emitting surface 212) is 3 mm ² . The light distribution pattern (light distribution) of a vehicle headlamp that is legally regulated in Japan is narrow in the vertical direction and wide in the horizontal direction. By making the cross section substantially rectangular), the light distribution pattern can be easily realized. The light emitting unit 7 does not have to be a rectangular parallelepiped, and may have a cylindrical shape in which the laser light irradiation surface 7a is an ellipse. Further, the laser light irradiation surface 7a is not necessarily a flat surface, and may be a curved surface. However, in order to control the reflection of the laser beam, the laser beam irradiation surface 7a is preferably a plane perpendicular to the optical axis of the laser beam. Furthermore, the area of the laser light irradiation surface 7a is preferably 1 to 3 mm ² .

  The light emitting unit 7 is located on the inner surface of the transparent plate 9 (on the side where the light emitting surface 212 is located) so as to face the light emitting surface 212 and to be the focal position of the reflecting mirror 8 (or the vicinity thereof). It is fixed to. The method for fixing the position of the light emitting unit 7 is not limited to this method, and the position of the light emitting unit 7 may be fixed by a rod-like or cylindrical member extending from the reflecting mirror 8.

  Thus, since the headlamp 1 irradiates the laser light emitted from the light emitting surface 212 in the horizontal direction on the laser light irradiation surface 7a, the entire lamp is included in the phosphor 7. The electrons in the low energy state are efficiently excited to the high energy state.

  As a result, the laser light emitted from the light emitting surface 212 is not concentrated on one point on the laser light irradiation surface 7a and is distributed and irradiated onto the laser light irradiation surface 7a via the truncated pyramid optical member 21. Therefore, it is possible to prevent the light emitting unit 7 from being deteriorated by irradiating the laser beams emitted from the respective semiconductor lasers 3 at the same point. Therefore, it is possible to provide the headlamp 1 that can realize high luminous flux, high luminance, and long life.

  The reflecting mirror 8 reflects incoherent light (hereinafter simply referred to as “light”) emitted from the light emitting unit 7 to form a light bundle that travels within a predetermined solid angle. That is, the reflecting mirror 8 reflects the light from the light emitting unit 7 to form a light beam that travels forward of the headlamp 1. The reflecting mirror 8 is, for example, a curved (cup-shaped) member having a metal thin film formed on the surface thereof, and opens in the traveling direction of the reflected light.

  In the present embodiment, the reflecting mirror 8 is hemispherical, and the center thereof is the focal position. Further, the opening of the reflecting mirror 8 is a plane perpendicular to the traveling direction of the light reflected by the reflecting mirror 8 (the traveling direction of the light emitted from the reflecting mirror 8 to the outside of the headlamp 1 (own device)). And an opening surface 8 a including the center of the reflecting mirror 8.

The area of the opening surface 8a is preferably 300 mm ² or more and less than 2000 mm ² (the diameter (optical system diameter) of the opening surface 8a is 19.5 mm or more and less than 50 mm). That is, it can be said that the size of the reflecting mirror 8 when viewed from the direction in which the light reflected by the reflecting mirror 8 is emitted (directly in front of the vehicle) is 300 mm ² or more and less than 2000 mm ² . Here, although the upper limit of the area of the opening surface 8a (values close to the upper limit) was 2000 mm ^2, more preferably from 1500 mm ² (diameter 43.7 mm). Although the lower limit of the area of the opening surface 8a was 300 mm ^2, more preferably from 500 mm ² (diameter 25.2 mm). The reason for this will be described later.

  The transparent plate 9 is a transparent resin plate that covers the opening of the reflecting mirror 8, and holds the light emitting unit 7. The transparent plate 9 is preferably formed of a material that blocks the laser light from the semiconductor laser 3 and transmits white light (incoherent light) generated by converting the laser light in the light emitting unit 7. In addition to the resin plate, an inorganic glass plate or the like can also be used. Most of the coherent laser light is converted into incoherent white light by the light emitting unit 7. However, there may be a case where a part of the laser beam is not converted for some reason. Even in such a case, the laser beam can be prevented from leaking to the outside by blocking the laser beam with the transparent plate 9. In addition, when such an effect is not expected and the light emitting unit 7 is held by a member other than the transparent plate 9, the transparent plate 9 can be omitted.

As described above, since the high-power laser beam is emitted from the semiconductor laser 3 to the light emitting unit 7 and the light emitting unit 7 can receive the laser light, the luminous flux emitted from the light emitting unit 7 is about 2000 lm, and A headlamp 1 having a high luminance and a high luminous flux with a luminance of the light emitting unit 7 of 100 cd / mm ² can be realized.

[Modification of Headlamp 1 (Part 1)]
Next, a modified example of the headlamp 1 will be described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of a headlamp 1 as a modification of the present embodiment. In addition, description is abbreviate | omitted about the structure similar to the headlamp 1 mentioned above.

  As shown in the figure, the headlamp 1 includes a semiconductor laser 3, an aspheric lens 4, a truncated cone-shaped optical member (light guide part) 22, a light emitting part 7, a reflecting mirror 8, and a transparent plate 9. The basic structure of the light emitting device is formed by the semiconductor laser 3, the truncated cone-shaped optical member 22, and the light emitting unit 7.

  The semiconductor laser 3 has 10 light emitting points (10 stripes) in one chip, and oscillates a laser beam of, for example, 405 nm (blue violet), an output of 11.2 W, an operating voltage of 5 V, and a current of 6.4 A. Which is enclosed in a 9 mm diameter package. The number of semiconductor lasers 3 enclosed in the package is one, and the power consumption at the time of the output is 32 W.

  The aspherical lens 4 is a lens for causing laser light (excitation light) oscillated from each semiconductor laser 3 to enter the light incident surface 221 that is one end of the truncated cone-shaped optical member 22. In the present embodiment, a rod lens is used as the aspheric lens 4.

  The frustoconical optical member 22 is a light guide member that condenses the laser light oscillated by the semiconductor laser 3 and guides it to the light emitting unit 7 (laser light irradiation surface 7 a), and the semiconductor laser 3 through the aspherical lens 4. And optically coupled. The frustoconical optical member 22 has a light incident surface 221 (incident end portion) that receives the laser light emitted from the semiconductor laser 3 and a light emitting surface 222 (emits the laser light incident from the light incident surface 221 to the light emitting portion 7. Output end).

The truncated cone-shaped optical member 22 is a tapered conical quartz (SiO ₂ ) light guide member (refractive index: 1.45). The light incident surface 221 (bottom) has a diameter of 10 mm, and the light exit surface 222 (top) has a diameter of 2 mm. Further, the side surface of the truncated cone-shaped optical member 22 is coated with a thermoplastic fluororesin (polytetrafluoroethylene: PTFE) having a refractive index of 1.35. The light incident surface 221 and the light output surface 222 may have a planar shape or a curved surface shape, similar to the light incident surface 211 and the light output surface 212.

  The frustoconical optical member 22 is corrected so that the aspect ratio of FFP (Far Field Pattern) is as close to a perfect circle as possible. Here, FFP refers to the light intensity distribution in a plane away from the light emitting point of the laser light source. In general, laser light emitted from a semiconductor light emitting device such as the semiconductor laser 3 or an edge-emitting diode has an angle of the emission intensity distribution of the active layer due to a diffraction phenomenon, and its FFP has an elliptical shape. For this reason, correction is necessary to make the FFP close to a perfect circle.

  Coupling efficiency of the aspherical lens 4 and the truncated cone-shaped optical member 22 (laser light emitted from the light emitting surface 222 of the truncated cone-shaped optical member 22 when the intensity of the laser beam emitted from the semiconductor laser 3 is 1) Strength) is 90%. For this reason, the 11.2 W laser light emitted from the semiconductor laser 3 is emitted as about 10 W laser light from the light emitting surface 222 after passing through the aspherical lens 4 and the truncated cone-shaped optical member 22.

  The light emitting unit 7 emits light upon receiving the laser light emitted from the light emitting surface 222, and includes the phosphor as described above. The light emitting unit 7 has a cylindrical shape with a diameter of 1.95 mm and a thickness of 1 mm.

As described above, also in the modified example, the light emitting unit 7 is irradiated with high-power laser light from the semiconductor laser 3, and the light emitting unit 7 can receive this laser light. Therefore, in this modification, a high-luminance and high-flux headlamp 1 (FIG. 2) is realized in which the luminous flux emitted from the light-emitting section 7 is about 1600 lm and the luminance of the light-emitting section 7 is 80 cd / mm ² . be able to.

[Modification of Headlamp 1 (Part 2)]
Next, another modification of the headlamp 1 will be described with reference to FIG. FIG. 3 is a diagram showing a schematic configuration of a headlamp 1 as another modification of the present embodiment. In addition, description is abbreviate | omitted about the structure similar to the headlamp 1 mentioned above.

  As shown in the figure, the headlamp 1 includes a semiconductor laser 3, a light guide (light guide unit) 23, a light emitting unit 7, a reflecting mirror 8, and a transparent plate 9. The basic structure of the light emitting device is formed by the semiconductor laser 3, the light guide 23 and the light emitting unit 7.

  The semiconductor laser 3 has five light emitting points (5 stripes) in one chip. For example, the semiconductor laser 3 oscillates a laser beam having a wavelength of 405 nm (blue purple) and has an output of 3.3 W, an operating voltage of 5 V, and a current of 2.22 A. It is enclosed in a 9 mm diameter package. As shown in FIG. 3, since the three semiconductor lasers 3 are mounted, the output of the semiconductor laser 3 as a whole is about 10 W, and the power consumption is 33.3 W (= 5 V × 2.22 A × 3).

  The light guide 23 is a light guide member that condenses the laser light oscillated by the semiconductor laser 3 and guides it to the light emitting unit 7 (laser light irradiation surface 7a). The light guide 23 is provided for each semiconductor laser 3 and is optically coupled to the semiconductor laser 3. The light guide 23 includes a light incident surface 231 (incident end portion) that receives the laser light emitted from the semiconductor laser 3 and a light emitting surface 232 (exit end portion) that emits the laser light incident from the light incident surface 231 to the light emitting portion 7. ). Similar to the light guide member described above, the cross-sectional area of the light emitting surface 232 is smaller than the cross-sectional area of the light incident surface 231, so that the laser light emitted from the semiconductor laser 3 can be condensed on the light emitting surface 232. it can.

  Further, as shown in the figure, the three light guides 23 are fixed so that the light emission surfaces 232 are aligned in a horizontal row, and may be in contact with the laser light irradiation surface 7a, or may be slightly spaced from each other. May be arranged.

  The light guide 23 is a tapered conical tube made of a thermoplastic fluororesin (polytetrafluoroethylene: PTFE), and is filled with a thermosetting acrylic resin (methyl methacrylate resin). The refractive index of PTFE is 1.35, and the refractive index of methyl methacrylate resin is 1.49. The diameter of the light incident surface 231 is 7 mm, and the diameter of the light emitting surface 232 is 1 mm. The light incident surface 231 and the light exit surface 232 may have a planar shape or a curved surface shape, similar to the light incident surface 211 and the light exit surface 212.

  The coupling efficiency of the light guide 23 (the intensity of the laser light emitted from the light emitting surface 232 of the light guide 23 when the intensity of the laser light emitted from the semiconductor laser 3 is 1) is 90%. For this reason, the 3.3 W (about 10 W) laser light emitted from the semiconductor laser 3 is emitted from the light emitting surface 232 as about 3 W (about 9 W) laser light after passing through the light guide 23.

As described above, also in a further modified example, the laser light of high output is irradiated from the semiconductor laser 3 to the light emitting unit 7, and the light emitting unit 7 can receive this laser light. Therefore, in this modification, a high-luminance and high-flux headlamp 1 (FIG. 3) is realized in which the luminous flux emitted from the light-emitting portion 7 is about 1800 lm and the luminance of the light-emitting portion 7 is 80 cd / mm ² . be able to.

[Range of output value of semiconductor laser 3]
Next, the output value range of the semiconductor laser 3 will be described. As described above, the headlamp 1 satisfies the high beam distribution characteristic standard. Further, the light intensity at the highest light intensity point in the high beam for vehicles defined by the current Japanese domestic law is defined as 29500 to 112500 cd (per light). The optical system area (area of the opening surface 8a) realized in this luminous intensity range and the necessary light source luminance (luminance of the light emitting unit 7) have the relationship shown in Table 1 below.

Note that light source luminance (cd / mm ² ) = luminous intensity (cd) / optical system area (mm ² ). In Table 1, the reflecting mirror 8 is not provided with the transparent plate 9 and the lens 12. That is, each value in Table 1 is calculated assuming that the optical system transmittance (the ratio of the light emitted to the outside of the headlamp 1 when the light reflected by the reflecting mirror 8 is 1) is 100%. ing.

As shown in Table 1, and emits light of the intensity range, and, in order to realize a headlamp 1 is the area of the opening surface 8a 2000 mm ^2, the luminance of the light emitting portion 7, from 14.8 to 56. Must be between 3 cd / mm ² . The inventors of the present invention have found that 600 to 3000 lm is required as the value of the light beam emitted from the light emitting unit 7 in order to realize this luminance. This width of 600 to 3000 lm is taken into consideration that it varies depending on the size of the light emitting portion 7. The value of the luminous flux indicates the value of the luminous flux radiated to the outside of the headlamp 1, and the headlamp 1 is provided with a transparent plate 9 and a lens 12, and the light passing through these (optical system). It is assumed that the transmittance (optical system transmittance) is 70%.

  In order to realize this light flux, the laser light output of the semiconductor laser 3 (the overall output when there are a plurality of semiconductor lasers 3) is 3 to 6 W in the case of the light flux 600 lm and 3000 lm in the case of 3000 lm. 15-30W is required. This output value varies depending on the optical system transmittance. For example, when the optical system transmittance 70% varies ± 20%, the output value varies within a range of ± 20%. Further, the operating voltage, current, etc. of the semiconductor laser 3 are determined according to this output value.

  Therefore, since the laser beam having the output value is output from the semiconductor laser 3, the light emitting unit 7 can emit light that satisfies the light intensity range of the highest light intensity point based on the domestic law.

[About the upper limit value and the lower limit value of the area of the opening surface 8a]
Next, the upper limit value and lower limit value of the area of the opening surface 8a will be described.

(About the upper limit)
The luminance of the halogen lamp that has been used as the conventional headlamp 1 is 20 to 25 cd / mm ² . As shown in Table 1, in order to realize the maximum value 112500 cd (upper limit value) of the maximum luminous intensity point based on the above domestic law, the area of the aperture (optical system area) is 4500-5625 mm ² or more. Is needed. Further, as the area of the aperture surface, a size of 2840 to 3550 mm ² or more is necessary to realize the intermediate value 71000 cd of the maximum luminous intensity point, and 2000 to cd smaller than the intermediate value 2000 to cd. A size of 2500 mm ² or more is required. Here, it is assumed that the halogen lamp has the same configuration as the headlamp 1. That is, it is assumed that the filament, which is the light emitting part of the halogen lamp, is provided at the same position as the light emitting part 7 and the light reflected by the reflecting mirror is emitted.

Here, the optical system transmittance in the conventional headlamp is generally about 0.6 to 0.75 (60 to 75%) (p. 1465 of Non-Patent Document 1). If the optical system transmittance is 0.6, the above-mentioned 50000 cd becomes 30000 cd by passing through the optical system. This 30000 cd is a value substantially equal to the minimum value 29500 cd (lower limit) of the luminous intensity at the highest luminous intensity point. That is, when a halogen lamp is used as a high beam headlamp, the area of the smallest aperture that can realize the lower limit of the luminous intensity at the highest luminous intensity point is 2000 mm ² . Therefore, in the case of a halogen lamp, even if the maximum luminance is 25 cd / mm ² , if the area of the opening surface is made smaller than 2000 mm ² , the luminous intensity range of the highest luminous intensity point cannot be satisfied. It can be said that there is a possibility.

On the other hand, in the headlamp 1 according to the present embodiment, as described above, since the luminance of the light emitting unit 7 is at least 80 cd / mm ² or more, even when the area of the opening surface is smaller than 2000 mm ² , even if the optical system transmits. Even if the rate is 60%, the lower limit of the luminous intensity at the highest luminous intensity point can be satisfied. Further, when the luminance of the light emitting unit 7 is 100 cd / mm ² , the upper limit value of the luminous intensity at the highest luminous intensity point can be satisfied even if the optical system transmittance is 60%.

Accordingly, in the headlamp 1, the area of the aperture surface that may not be able to satisfy the luminous intensity range of the highest luminous intensity point using a conventional halogen lamp, that is, the upper limit value of the area of the aperture surface 8a (closest to the upper limit value). Value) can be 2000 mm ² .

Moreover, HID (luminance 75cd / mm < ² >) may be used as a conventional headlamp. In order to realize the upper limit of the luminous intensity at the highest luminous intensity point with the head lamp (HID lamp) using this HID, as shown in Table 1, the area of the opening surface needs to be 1500 mm ² or more. It becomes. It is assumed that the HID lamp has the same configuration as the headlamp 1 as with the halogen lamp. That is, it is assumed that an arc tube (light-emitting tube) which is a light-emitting portion of the HID lamp is provided at the same position as the light-emitting portion 7 and light reflected by the reflecting mirror is emitted.

That is, in the case of a conventional HID lamp, it can be said that if the area of the opening surface is smaller than 1500 mm ² , the upper limit value of the luminous intensity at the highest luminous intensity point cannot be satisfied. For this reason, using the case of the conventional HID lamp, the area of the aperture surface that may not be able to satisfy the luminous intensity range of the highest luminous intensity point, that is, the upper limit value of the aperture area (the value closest to the upper limit value) It can be said that it is more preferable to set it as 1500 mm < ² >.

  Here, the HID includes at least an arc tube (arc tube) made of quartz glass and two discharge electrodes that supply current to the inside of the arc tube. The discharge electrode extends from both ends of the arc tube to the vicinity of the light emitting point, and an atmospheric gas such as mercury or argon gas is enclosed in the arc tube as a light emitting substance. In the HID, when a current flows between the discharge electrodes, a discharge action occurs at the light emitting point, and the light emitting material emits light.

  Since HID emits a luminescent material by electric discharge, light with a constant luminous intensity cannot be emitted unless the arc tube is heated to such an extent that electric discharge occurs. For this reason, the HID lamp takes a certain time (about 4 to 8 minutes) from when the lighting switch is turned on until light having a constant luminous intensity is emitted, and cannot be turned on instantaneously (instant lighting property). Not good). HID lamps used in automotive headlamps are being improved in this regard, but HID lamps are still practical as high-beam headlamps that require so-called passing that can be switched on / off instantaneously. Is low.

Moreover, since HID needs to be provided with at least an arc tube and two discharge electrodes, it is difficult to make it smaller than a predetermined size. For this reason, it is difficult for the HID lamp to be smaller than 1500 mm ^{2 in} consideration of the light emission efficiency (efficiency of the optical system) described later.

From the above, the area of the opening surface 8a in the headlamp 1 is to satisfy the luminous intensity range of the highest luminous intensity point in the case of realizing a high-beam headlamp that does not have any particular problems of HID such as instantaneous lighting performance. , it would be preferable to be smaller than 2000 mm ^2. Moreover, when the problem which the said HID has is not considered, in order to satisfy the luminous intensity range of the said highest luminous intensity point, it can be said that it is preferable to make it smaller than 1500 mm < ² >.

In addition, since the arc tube and the two discharge electrodes block the passage of light generated at the light emission point (that is, a shadowed portion is formed), the HID has a corresponding decrease in luminance. Therefore, it is difficult for the HID lamp to have a configuration that takes advantage of the high brightness unique to HID. That is, the luminance of the HID lamp is actually a value smaller than 60-80 cd / mm ² described in Non-Patent Document 1. On the other hand, since the headlamp 1 does not have a shadowed portion as described above, the obtained luminance can be fully utilized.

  Further, in the case of HID, a circuit (ballast) for controlling lighting of the HID is required, but the headlamp 1 does not need to be provided with such a circuit and can be manufactured at a lower cost than the HID lamp. .

  In the above description, the area of the opening surface 8a in the headlamp 1 can be made smaller than the area of the opening surface in the conventional lighting device. Therefore, the headlamp 1 is overwhelming compared to the conventional lighting device. This is to explain that the size can be reduced. Therefore, the area of the opening surface 8a in the headlamp 1 is not limited to the above-described area, but can be arbitrarily set. The same applies to the later-described (lower limit value).

(About the lower limit)
In headlamp 1, since the area of the laser beam irradiated surface 7a (the size of the light emitting portion 7) is, for example, 1 to 3 mm ² and finite, if the area of the opening surface 8a is smaller than 300 mm ^2, the light emitting portion 7 becomes relatively large with respect to the reflecting mirror 8. For this reason, there is a possibility that the light radiation efficiency (efficiency of the optical system) in the reflecting mirror 8 is reduced. The inventors of the present invention have obtained an experimental result that when the ratio of the size of the light emitting portion 7 to the area of the opening surface 8a is smaller than 1: 100 (3 mm ² : 300 mm ² ), the radiation efficiency is extremely reduced ( In the present specification, the fact that the denominator becomes small is referred to as “the ratio becomes small”. Therefore, the area of the opening surface 8a is preferably 300 mm ² or more.

Furthermore, it has been found that when the ratio is 1: 150 or more, highly practical radiation efficiency can be obtained. Therefore, when the size of the laser beam irradiated surface 7a and 3 mm ^2, it can be said that it is preferable area of the opening surface 8a is 500 mm ² or more.

From Table 1 and the lower limit value of the area of the opening surface 8a, the upper limit value of the luminance of the light-emitting portion 7 is 375 cd / mm ² (when the area of the opening surface 8a is 300 mm ² ), and 225 cd / mm ² (opening) the area of the surface 8a is said that it is preferable that when the 500 mm ^2).

(Comparison with conventional headlamps)
Here, a comparative example with a conventional headlamp will be described with reference to FIG. FIG. 4 is a diagram showing the relationship between the brightness of a vehicle (automobile) headlamp using each light source and the optical system area of the headlamp. Here, the light intensity required for the headlamp (one lamp) is 100,000 cd (100,000 cd), and the optical system transmittance is 70%. That is, FIG. 4 shows a comparison result in a general high beam headlamp 1.

As shown in the drawing, in the case of a halogen lamp (or LED) having a luminance of 25 cd / mm ² , the area of the opening surface needs to be about 5000 mm ² in order to realize emission of light having a luminous intensity of 100,000 cd. In the case of an HID lamp having a luminance of 75 cd / mm ² , the area of the opening surface needs to be 2000 mm ² .

However, as described above, since it is difficult to make use of the high luminance due to the configuration of the HID, there is a possibility that the high luminance HID of 75 cd / mm ² cannot actually be realized. In addition, since it cannot be smaller than a predetermined size, the area of the opening surface may not be smaller than 2000 mm ² depending on the light radiation efficiency (efficiency of the optical system). Furthermore, when the optical system transmittance is 60%, the area of the opening surface needs to be 2222 mm ² .

That is, in the case of HID, it is theoretically possible to set the area of the opening surface to 2000 mm ² , but it is understood that this is not always a realizable value.

On the other hand, in the headlamp 1 according to the present invention, since the luminance of the light emitting unit 7 is 75 cd / mm ² or more, even if the optical system transmittance is 60% in order to realize the emission of light with a luminous intensity of 100,000 cd. It can be seen that the area of the opening surface 8a may be smaller than 2000 mm ² . In other words, in the headlamp 1, when the emission of light having a luminous intensity of 100000 cd is realized using an optical system having an optical system transmittance of 70%, the area of the opening surface 8a may be smaller than 2000 mm ² .

As described above, the headlamp 1 includes the semiconductor laser 3 that emits laser light, the light emitting unit 7 that emits light by receiving the laser light emitted from the semiconductor laser 3, and the reflection that reflects the light emitted from the light emitting unit 7. And a mirror 8. The luminance of the light emitting portion 7 is greater than 25 cd / mm ^2, the area of the vertical opening surface in the traveling direction of the light emitted in the reflection mirror 8, outside of the headlamp 1 is 2000 mm ² smaller. In other words, it can be said that the luminance of the light emitting unit 7 is larger than 25 cd / mm ^{2 and} the area of the image of the reflecting mirror onto which the light reflected by the reflecting mirror 8 is projected is smaller than 2000 mm ² .

For example, when a conventional halogen lamp is used as a high-beam headlamp, the area of the opening surface may not be smaller than 2000 mm ² when emitting light that satisfies the minimum value of light intensity defined above. There is. However, in the headlamp 1, since the luminance of the light emitting unit 7 is larger than 25 cd / mm ² which is the maximum luminance that can be realized by the halogen lamp, even if the area of the opening surface 8a is smaller than 2000 mm ² , the luminous intensity defined as a high beam. Light that satisfies the range can be emitted.

That is, when a halogen lamp is used as a headlamp and emits light having a luminous intensity of about 29500 cd, there is a possibility that the area of the opening surface cannot be made smaller than 2000 mm ² . On the other hand, in the headlamp 1, since the luminance of the light emitting part is larger than 25 cd / mm ² which is the maximum luminance that can be realized by the halogen lamp, even if the area of the opening surface is smaller than 2000 mm ² , for example, the luminous intensity range of 29500 to 112500 cd is obtained. Filling light can be emitted.

Further, although there is an HID lamp having a luminance of 75 cd / mm ² as a high-intensity light source, the HID lamp has a problem that it is not excellent in instantaneous lighting performance, and it has been found that it is not suitable for a headlamp for a high beam. That is, the HID lamp is not suitable for a vehicle headlamp that requires instantaneous lighting performance.

  Therefore, the headlamp 1 can be designed to be overwhelmingly smaller than a conventional lighting device in consideration of practicality. That is, the headlamp 1 smaller than the conventional lighting device can be realized.

Further, even when the HID lamp is used as a high beam headlamp, from Table 1, if the area of the aperture surface is made smaller than 1500 mm ² , light satisfying the luminous intensity range defined as the high beam can be emitted. It becomes impossible. However, in the headlamp 1, the luminance of the light emitting unit 7 is larger than 75 cd / mm ^2, which is a maximum luminance at a practical level that can be realized by an HID lamp, so even if the area of the opening surface 8 a is smaller than 1500 mm ^2. It is possible to emit light satisfying the luminous intensity range defined as a high beam. That is, the headlamp 1 can realize the area of the opening surface 8a that cannot be realized by the HID lamp even when the HID lamp having low practicality is used as the high beam.

That is, from Table 1, for example, when an HID lamp having a higher luminance than a halogen lamp is used as a head lamp and light is emitted in a luminous intensity range of 29500 to 112500 cd, for example, if the area of the aperture is smaller than 1500 mm ² , the luminous intensity It becomes impossible to emit light satisfying the range. On the other hand, since the headlamp 1 has a brightness higher than the maximum brightness of 75 cd / mm ^2, which is a practical level of the HID lamp, even if the area of the opening surface is smaller than 1500 mm ² , the headlamp 1 emits light that satisfies the luminous intensity range. be able to. Therefore, a smaller headlamp 1 can be realized.

  In addition, since the headlamp 1 is mounted on a vehicle as a high beam, a high beam that is smaller than the conventional one can be realized, and thus the degree of freedom in designing the vehicle can be increased.

Here, the illuminating device of Patent Document 3 that emits light having luminance and color rendering properties similar to those of a halogen lamp with a luminous flux of about 1200 lumens (lm) and a luminance of about 25 cd / mm ² is compared with the headlamp 1. The luminous flux is inferior and the luminance is 1/3 or less. Therefore, in order to achieve the same level of brightness as the halogen lamp 1 using the illumination device of Patent Document 3, at least three illumination devices are required. Therefore, it can be seen that the halogen lamp 1 realizes an overwhelmingly small high-beam illumination device as compared with the illumination device of Patent Document 3.

(Power saving realized by halogen lamp 1)
Here, advantages of the headlamp 1 will be described from another viewpoint.

  As described above, the headlamp 1 can be reduced in size as compared with the conventional lighting device. And with miniaturization of an illuminating device, size reduction of structural members, such as the reflective mirror 8 and the transparent plate 9, is also implement | achieved. That is, the headlamp 1 can also be reduced in weight compared to the conventional lighting device.

  Furthermore, the headlamp 1 also achieves higher brightness and higher luminous flux than conventional lighting devices. Therefore, if the headlamp 1 is used to achieve the same level of luminance and luminous flux as that of the conventional illumination device, the output of the semiconductor laser 3 may be lowered, and thereby the luminance and luminous flux equivalent to that of the conventional illumination device. Is realized. That is, the headlamp 1 can realize a reduction in power consumption.

  In consideration of the recent increase in environmental awareness, the headlamp 1 can be applied to a vehicle headlight very suitably. That is, since the headlamp 1 has been reduced in size and weight, it is excellent in usability and can greatly increase the degree of freedom in designing the vehicle. In addition, the fuel efficiency of the vehicle is improved due to the weight reduction. In addition, since the headlamp 1 can reduce power consumption, it can greatly contribute to reduction of power consumption in the vehicle.

  As described above, the headlamp 1 is not only reduced in size as compared with the conventional lighting device, but also can realize merits such as power saving and improved fuel efficiency when applied to a vehicle headlight. .

(Structure of semiconductor laser 3)
Here, the basic structure of the semiconductor laser 3 will be described. FIG. 5A schematically shows a circuit diagram of the semiconductor laser 3, and FIG. 5B is a perspective view showing a basic structure of the semiconductor laser 3. As shown in the figure, the semiconductor laser 3 has a configuration in which a cathode electrode 19, a substrate 18, a cladding layer 113, an active layer 111, a cladding layer 112, and an anode electrode 17 are laminated in this order.

The substrate 18 is a semiconductor substrate, and it is preferable to use GaN, sapphire, or SiC in order to obtain blue to ultraviolet excitation light for exciting the phosphor as in the present application. In general, as other examples of a substrate for a semiconductor laser, a group IV semiconductor represented by a group IV semiconductor such as Si, Ge and SiC, GaAs, GaP, InP, AlAs, GaN, InN, InSb, GaSb and AlN Group V compound semiconductors, Group II-VI compound semiconductors such as ZnTe, ZeSe, ZnS and ZnO, oxide insulators such as ZnO, Al ₂ O ₃ , SiO ₂ , TiO ₂ , CrO ₂ and CeO ₂ , and SiN Any material of the nitride insulator is used.

  The anode electrode 17 is for injecting current into the active layer 111 through the cladding layer 112.

  The cathode electrode 19 is for injecting current into the active layer 111 from the lower part of the substrate 18 through the clad layer 113. The current is injected by applying a forward bias to the anode electrode 17 and the cathode electrode 19.

  The active layer 111 has a structure sandwiched between the clad layer 113 and the clad layer 112.

  As the material for the active layer 111 and the cladding layer, a mixed crystal semiconductor made of AlInGaN is used to obtain blue to ultraviolet excitation light. Generally, a mixed crystal semiconductor mainly composed of Al, Ga, In, As, P, N, and Sb is used as an active layer / cladding layer of a semiconductor laser, and such a configuration may be used. Moreover, you may be comprised by II-VI group compound semiconductors, such as ZnMgSSeTe and ZnO.

  The active layer 111 is a region where light emission is caused by the injected current, and the emitted light is confined in the active layer 111 due to a difference in refractive index between the cladding layer 112 and the cladding layer 113.

  Further, the active layer 111 is formed with a front side cleaved surface 114 and a back side cleaved surface 115 provided to face each other in order to confine light amplified by stimulated emission, and the front side cleaved surface 114 and the back side cleaved surface 115. Plays the role of a mirror.

  However, unlike a mirror that completely reflects light, when a part of the light amplified by stimulated emission is amplified to some extent, either the front side cleavage surface 114 or the back side cleavage surface 115 of the active layer 111 is selected. (In this embodiment, it is emitted from the front side cleavage surface 114 for the sake of convenience) and becomes the excitation light L0. Note that the active layer 111 may form a multilayer quantum well structure.

  Note that a reflective film (not shown) for laser oscillation is formed on the back side cleaved surface 115 opposite to the front side cleaved surface 114, and the difference in reflectance between the front side cleaved surface 114 and the back side cleaved surface 115 is different. By providing, for example, most of the excitation light L0 can be emitted from the light emitting point 103 from the front-side cleavage surface 114 which is a low reflectance end face.

  The clad layer 113 and the clad layer 112 are made of n-type and p-type GaAs, GaP, InP, AlAs, GaN, InN, InSb, GaSb, and AlN group III-V compound semiconductors, and ZnTe, ZeSe. , ZnS, ZnO, and other II-VI group compound semiconductors, and by applying a forward bias to the anode electrode 17 and the cathode electrode 19, current can be injected into the active layer 111. It has become.

  As for film formation with each semiconductor layer such as the clad layer 113, the clad layer 112, and the active layer 111, MOCVD (metal organic chemical vapor deposition) method, MBE (molecular beam epitaxy) method, CVD (chemical vapor deposition) method. The film can be formed using a general film forming method such as a laser ablation method or a sputtering method. The film formation of each metal layer can be configured using a general film forming method such as a vacuum deposition method, a plating method, a laser ablation method, or a sputtering method.

(Light emission principle of the light emitting unit 7)
Next, the light emission principle of the phosphor by the laser light oscillated from the semiconductor laser 3 will be described.

  First, the laser light oscillated from the semiconductor laser 3 is irradiated onto the phosphor included in the light emitting unit 7, whereby electrons existing in the phosphor are excited from a low energy state to a high energy state (excited state).

  Since this excited state is unstable, the energy state of the electrons in the phosphor is changed to the original low energy state after a certain time (the energy state of the ground level or the level between the excited level and the ground level). Transition to a stable level energy state).

  In this way, the phosphors emit light when electrons excited to the high energy state transition to the low energy state.

  White light can be composed of a mixture of three colors that satisfy the principle of equal colors, or a mixture of two colors that satisfy the relationship of complementary colors. Based on this principle, the color of the laser light emitted from the semiconductor laser 3 and the phosphor White light can be generated by combining the color of the light emitted by the light as described above.

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

(Configuration of the headlamp 1a)
First, the structure of the headlamp (vehicle headlamp) 1a according to the present embodiment will be described with reference to FIG. FIG. 6 is a sectional view showing another configuration of the headlamp 1 according to the first embodiment and the configuration of a headlamp 1a which is a projector-type headlamp. This headlamp 1a is another example of a configuration for realizing a headlamp that is smaller than a conventional headlamp, and is a projector-type headlamp, and a truncated pyramid-shaped optical member 21, a truncated cone shape. It differs from the headlamp 1 in that an optical fiber 5 is provided instead of the optical member 22 and the light guide 23.

  As shown in the figure, the headlamp 1a includes a semiconductor laser array (excitation light source) 2, an aspherical lens 4, an optical fiber (light guide part) 5, a ferrule 6, a light emitting part 7, a reflecting mirror 8, a transparent plate 9, and a housing. 10, an extension 11, a lens 12, a convex lens 14, and a lens holder 16. The semiconductor laser array 2, the optical fiber 5, the ferrule 6 and the light emitting unit 7 form a basic structure of the light emitting device. Since the headlamp 1a is a projector-type headlamp, the headlamp 1a includes a convex lens 14. The present invention may be applied to other types of headlamps (for example, semi-shielded beam headlamps), in which case the convex lens 14 can be omitted. The description of the portions of the aspheric lens 4, the light emitting unit 7, the reflecting mirror 8, and the transparent plate 9 having the same functions as those provided in the headlamp 1 is omitted here.

  The semiconductor laser array 2 functions as an excitation light source that emits excitation light, and includes a plurality of semiconductor lasers (semiconductor laser elements) 3 on a substrate. Note that the configuration of the semiconductor laser 3 is the same as that of the semiconductor laser 3 included in the headlamp 1, and therefore the description thereof is omitted here.

  The aspherical lens 4 is a lens for causing laser light (excitation light) oscillated from the semiconductor laser 3 to enter an incident end 5 b that is one end of the optical fiber 5.

  The optical fiber 5 is a light guide member that guides the laser light oscillated by the semiconductor laser 3 to the light emitting unit 7 and is a bundle of a plurality of optical fibers. The optical fiber 5 has a plurality of incident end portions 5b that receive the laser light and a plurality of emission end portions 5a that emit the laser light incident from the incident end portion 5b. The plurality of emission end portions 5 a emit laser beams to different regions on the laser beam irradiation surface (light receiving surface) 7 a (see FIG. 7) of the light emitting unit 7. In other words, the plurality of emission end portions 5 a emit laser beams to different portions of the light emitting unit 7. The emission end 5a may be in contact with the laser light irradiation surface 7a, or may be disposed at a slight interval. More specifically, the portions with the highest light intensity in the light intensity distributions of the laser beams emitted from the plurality of emission end portions 5 a are irradiated to the different portions of the light emitting unit 7.

  Here, the laser beam emitted from one emitting end portion 5a reaches the laser beam irradiation surface 7a while spreading at a predetermined angle. Further, when laser beams are emitted from the plurality of emission end portions 5a, a plurality of irradiation regions are formed on the laser beam irradiation surface 7a. Therefore, even if the emission end portions 5a of the plurality of optical fibers 5 are arranged side by side in a plane parallel to the laser light irradiation surface 7a, the irradiation region formed by the laser light from these emission end portions 5a , May overlap each other.

  Even in such a case, the place where the light intensity is the highest in the light intensity distribution of the laser light emitted from the emission end portion 5a (the central portion of the irradiation region formed by each laser light on the laser light irradiation surface 7a (the maximum light intensity portion). )) Is emitted to different portions of the laser light irradiation surface 7a of the light emitting section 7, the laser light can be irradiated to the laser light irradiation surface 7a in a two-dimensionally distributed manner.

  That is, the position of the maximum light intensity portion that is the portion with the highest light intensity in the projection image formed by irradiating the light emitting portion 7 with the laser light emitted from one of the plurality of emission end portions 5a. What is necessary is just to differ from the position of the maximum light intensity part of the projection image originating in the other output end part 5a. Therefore, it is not always necessary to completely separate the irradiated areas from each other.

  The optical fiber 5 has a two-layer structure in which an inner core is covered with a clad having a refractive index lower than that of the core. The core is mainly composed of quartz glass (silicon oxide) having almost no absorption loss of laser light, and the clad is composed mainly of quartz glass or a synthetic resin material having a refractive index lower than that of the core. . For example, the optical fiber 5 is made of quartz having a core diameter of 200 μm, a cladding diameter of 240 μm, and a numerical aperture NA of 0.22. However, the structure, thickness, and material of the optical fiber 5 are limited to those described above. Instead, the cross section perpendicular to the long axis direction of the optical fiber 5 may be rectangular.

  In addition, you may use what combined members other than an optical fiber, or an optical fiber and another member as a light guide member. The light guide member only needs to have at least one incident end that receives laser light oscillated by the semiconductor laser 3 and a plurality of emission ends that emit laser light incident from the incident end. For example, an incident part having at least one incident end part and an emitting part having a plurality of outgoing end parts may be formed as members different from the optical fiber, and the incident part and the outgoing part may be connected to both ends of the optical fiber. Good.

  FIG. 7 is a diagram illustrating a positional relationship between the emission end portion 5 a and the light emitting portion 7. As shown in the figure, the ferrule 6 holds a plurality of emission end portions 5 a of the optical fiber 5 in a predetermined pattern with respect to the laser light irradiation surface 7 a of the light emitting unit 7. The ferrule 6 may be formed with holes for inserting the emission end portion 5a in a predetermined pattern, and can be separated into an upper part and a lower part, and is formed on the upper and lower joint surfaces, respectively. The exit end portion 5a may be sandwiched by a groove.

  The ferrule 6 may be fixed to the reflecting mirror 8 by a rod-like or cylindrical member extending from the reflecting mirror 8. The material of the ferrule 6 is not specifically limited, For example, it is stainless steel. In FIG. 7, three emission end portions 5a are shown in accordance with the number of semiconductor lasers 3 (that is, the number of optical fibers 5), but the number of emission end portions 5a is not limited to three.

  The light emitting section 7 emits light upon receiving the laser light emitted from the emission end 5a, and includes a phosphor that emits light upon receiving the laser light. Further, the light emitting unit 7 is disposed in the vicinity of a first focal point of a reflecting mirror 8 to be described later, and as shown in FIG. 6, on the surface inside the transparent plate 9 (on the side where the emitting end portion 5 a is located), the emitting end is formed. It is fixed at a position facing the portion 5a.

  FIG. 8 is a cross-sectional view showing a modified example of the positioning method of the light emitting unit 7. As shown in the figure, the light emitting section 7 may be fixed to the tip of a cylindrical section 15 extending through the center of the reflecting mirror 8. In this case, the emission end portion 5 a of the optical fiber 5 can be passed through the cylindrical portion 15. Further, in this configuration, the transparent plate 9 can be omitted.

  The reflecting mirror 8 is a member having, for example, a metal thin film formed on the surface thereof, and reflects the light emitted from the light emitting unit 7 so as to converge the light at its focal point. Since the headlamp 1a is a projector-type headlamp, the basic shape of the reflecting mirror 8 has an elliptical cross section parallel to the optical axis direction of the reflected light. The reflecting mirror 8 has a first focal point and a second focal point, and the second focal point is located closer to the opening of the reflecting mirror 8 than the first focal point. The convex lens 14 to be described later is arranged so that its focal point is located in the vicinity of the second focal point, and projects the light converged to the second focal point by the reflecting mirror 8 forward.

  In the present embodiment, the opening of the reflecting mirror 8 has a plane perpendicular to the traveling direction of the light emitted from the convex lens 14 (the optical axis direction of the convex lens 14) (the headlamp 1a of the reflecting mirror 8). A plane perpendicular to the traveling direction of the light emitted to the outside of the apparatus) and an opening surface 8b including the minor axis of the elliptical reflecting mirror 8.

  The transparent plate 9 is a transparent resin plate that covers the opening of the reflecting mirror 8, and holds the light emitting unit 7. That is, the light emitting unit 7 is held by the transparent plate 9 so as to be installed in the vicinity of the first focal point of the reflecting mirror 8.

  The housing 10 forms the main body of the headlamp 1a and houses the reflecting mirror 8 and the like. The optical fiber 5 passes through the housing 10, and the semiconductor laser array 2 is installed outside the housing 10. The semiconductor laser array 2 generates heat when the laser light is oscillated, but the semiconductor laser array 2 can be efficiently cooled by being installed outside the housing 10. Moreover, since the semiconductor laser 3 may break down, it is preferable to install it at a position where it can be easily replaced. If these points are not taken into consideration, the semiconductor laser array 2 may be accommodated in the housing 10.

  The extension 11 is provided on the front side of the reflecting mirror 8 to improve the appearance by concealing the internal structure of the headlamp 1a and enhance the sense of unity between the reflecting mirror 8 and the vehicle body. The extension 11 is also a member having a metal thin film formed on the surface thereof, like the reflecting mirror 8.

  The lens 12 is provided in the opening of the housing 10 and seals the headlamp 1a. The light emitted from the light emitting unit 7 is emitted to the front of the headlamp 1 through the lens 12.

  The convex lens 14 collects the light emitted from the light emitting unit 7 and projects the collected light to the front of the headlamp 1. The focal point of the convex lens 14 is in the vicinity of the second focal point of the reflecting mirror 8, and its optical axis is substantially the center of the light emitting surface (the surface on the convex lens 14 side (the side held by the transparent plate 9)) of the light emitting unit 7. Is located. The convex lens 14 is held by a lens holder 16 and a relative position with respect to the reflecting mirror 8 is defined.

  The convex lens 14 is normally held by the lens holder 16 so that the cross-sectional size of the convex lens 14 is perpendicular to the optical axis direction of the convex lens 14 and is smaller than the opening surface 8b. It is not limited. That is, the lens holder 16 may be provided in parallel to the optical axis direction, and the cross section of the convex lens 14 and the area of the opening surface 8b may be the same.

  That is, “the area of the opening surface of the reflecting mirror 8 perpendicular to the traveling direction of the light emitted to the outside of the headlamp 1” in the present embodiment means that the section of the convex lens 14 is smaller than the opening surface 8b. The area of the cross section shall be indicated. That is, in this case, the reflecting mirror 8 and the lens holder 16 are integrated, and the opening surface 8c (corresponding to the cross section of the convex lens 14) formed by the lens holder 16 on which the convex lens 14 is provided is referred to as “reflecting mirror”. 8 open surfaces ". On the other hand, when the areas of the opening surface 8b and the opening surface 8c are the same, the area of the opening surface 8b may be indicated as “the area of the opening surface”. That is, it can be said that the “area of the opening surface” is a cross-sectional area of a portion where the light reflected by the reflecting mirror 8 is emitted.

The “area of the opening surface” according to the present embodiment is 300 mm ² or more and less than 2000 mm ² (preferably 500 mm ² or more and less than 1500 mm ² ) as in the case of the opening surface 8a, and the lower limit is 100 mm ^2. May be. In other words, the area of the image of the reflecting mirror 8 to the light reflecting mirror 8 is reflected is projected is smaller than 300 mm ² or more 2000 mm ² (preferably less than 500 mm ² or more 1500 mm ^2), the lower limit of 100 mm ² It can be said that it may be.

As described above, also in the present embodiment, the light emitting unit 7 is irradiated with the high-power laser light from the semiconductor laser 3 and the light emitting unit 7 can receive the laser light. 7 can realize a high-luminance and high-flux headlamp 1a in which the luminous flux emitted from the luminous flux 7 is about 2000 lm and the luminance of the light-emitting portion 7 is 100 cd / mm ² .

Therefore, the projector-type headlamp 1a has an implementation luminance of at least 75 cd / mm ² , and in consideration of practicality, realizes a high-beam illumination device that is smaller than a conventional illumination device. Can do. Further, when the area of the opening surface 8b or the opening surface 8c is smaller than 1500 mm ² , the opening surface 8b that cannot be realized by the HID lamp even if a low practical HID lamp is used as the high beam. The opening surface 8c can be realized. That is, since the headlamp 1a has a brightness higher than the maximum brightness of 75 cd / mm ² which is a practical level of the HID lamp, even if the area of the opening surface is made smaller than 1500 mm ² , for example, the light intensity range of 29500 to 112500 cd is satisfied. Light can be emitted. Therefore, a smaller headlamp 1a can be realized.

[Modification of Headlamps 1 and 1a]
Although the above-described headlamps 1 and 1a according to the first and second embodiments have been described as satisfying the high beam light distribution characteristic standard, they may be used as low-light headlights for automobiles.

  In this case, the headlamps 1 and 1a only need to be configured to satisfy the light distribution characteristic standard of the headlight for passing for automobiles. For example, the headlamps 1 and 1a have the shape of the light irradiation region defined by the light distribution characteristic standard. You may provide the light emission part which has the light emission surface of a corresponding shape. Further, in the case of a projector-type headlamp such as the headlamp 1a, between the light emitting portion and a convex lens that projects light emitted from the light emitting portion (light reflected by the reflecting mirror) to the front of the vehicle, There may be provided a light shielding plate that is molded so as to satisfy the light distribution characteristic standard required for the passing headlamp. In addition, when the headlamp 1a includes both the light emitting portion having the light emitting surface having the above shape and the light shielding plate, it is possible to prevent the projected image from being blurred at a portion away from the optical axis of the convex lens. is there.

  Next, with reference to FIG. 9, the light distribution characteristic required for a vehicle headlight will be described.

  FIG. 9 (a) is a diagram showing the light distribution characteristics required for a vehicle headlight (notification [2008.10.15], Annex 51) that defines the details of safety standards for road transport vehicles. Excerpt from headlamp device type specification criteria). This figure shows an image of light projected on the screen when light from a passing headlamp is irradiated on a screen installed vertically at a position 25 m ahead of the automobile.

  In FIG. 9A, the zone I is a region below the horizontal straight line located 750 mm below the straight line hh that is a horizontal reference straight line. At an arbitrary point in the zone I, it is required that the illuminance is not more than twice the actual measurement value at the point of 0.86D-1.72L.

  Zone III is an area above a white area (referred to as a bright area). At any point in the zone III, 0.85 lx (lux) or less is required. That is, this zone III is a region (dark region) where it is required to suppress the illuminance below a predetermined illuminance so that the light beam does not interfere with other traffic. The boundary line between the zone III and the bright region includes a straight line 21 that forms an angle of 15 degrees with respect to the straight line hh and a straight line 22 that forms an angle of 45 degrees with respect to the straight line hh.

  The zone IV is a total of 4 horizontal straight lines located 375 mm below the straight line hh, horizontal straight lines located 750 mm below the straight line hh, and two vertical straight lines located 2250 mm to the left and right of the straight line VV which is the vertical reference straight line. It is an area surrounded by a straight line. It is required that the illuminance is 3 lx or more at an arbitrary point in the zone IV. That is, the zone IV is a brighter region among the bright regions that are regions between the zone I and the zone III.

  FIG.9 (b) is a figure which shows the illumination intensity prescribed | regulated to the light distribution characteristic reference | standard of the passing headlamp. As shown in the figure, at two points of point 0.6D-1.3L and point 0.86D-1.72L, higher illuminance is required than the surroundings. These two points correspond to the vicinity in front of the host vehicle, and these two points are required to be able to confirm obstacles in the traveling direction even at night.

[Another expression of the present invention]
The present invention can also be expressed as follows.

  An object of the present invention is to provide a headlight (laser headlight) that is reduced in size as compared with a conventional in-vehicle headlight.

  The laser headlight according to the present invention is capable of emitting a light beam of 600 lm by combining an excitation light source made of a semiconductor laser capable of high-power oscillation and a light emitting unit that emits light by excitation light from the excitation light source, and By combining a laser illumination light source that achieves a luminance of 75 cd / mm 2 and an optical system consisting of a mirror and a lens, the head is overwhelmingly smaller than in the past while obtaining brightness equivalent to or higher than that of a conventional vehicle headlight. It is characterized by realizing light (for high beam).

[Supplement]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  For example, a high-power LED may be used as the excitation light source. In this case, a light emitting device that emits white light can be realized by combining an LED that emits light having a wavelength of 450 nm (blue) and a yellow phosphor or green and red phosphors. Further, the LED in this case needs to have an output equivalent to or higher than that of the semiconductor laser provided in the vehicle headlamp according to the present invention.

  As the excitation light source, a solid-state laser other than a semiconductor laser, for example, a light emitting diode capable of high-power oscillation may be used. However, it is preferable to use a semiconductor laser because the excitation light source can be reduced in size.

  Further, a configuration in which the semiconductor laser 3 and the light emitting unit 7 are integrally sealed so that the laser light from the semiconductor laser 3 is appropriately applied to the laser light irradiation surface 7a of the light emitting unit 7 (no light guide member is required). Configuration).

  Further, the opening surfaces 8a and 8b of the reflecting mirror 8 are circular when viewed from the front of the vehicle. However, the present invention is not limited to this. If the light reflected by the reflecting mirror 8 is efficiently emitted to the outside, an ellipse or It may be a rectangle or the like.

  The present invention is an illuminating device that is reduced in size as compared with a conventional illuminating device, and can be applied particularly to a headlamp for a vehicle.

1, 1a Headlamp (vehicle headlamp, traveling headlamp)
3 Semiconductor laser (excitation light source)
5 Optical fiber (light guide)
5a Emission end portion 5b Incident end portion 7 Light emitting portion 8 Reflecting mirror 8a, 8b, 8c Opening surface 21 Frustum-shaped optical member (light guide portion)
22 frustoconical optical member (light guide)
23 Light guide (light guide)
211, 221, 231 Light incident surface (incident end)
212, 222, 232 Light exit surface (exit end)

Claims (5)

An excitation light source that emits excitation light;
A light emitting unit that emits light in response to excitation light emitted from the excitation light source;
A reflecting mirror that reflects the light emitted by the light emitting unit,
The luminous flux emitted from the light emitting unit is larger than 600 lm,
The vehicular headlamp characterized in that the luminance of the light emitting unit is greater than 75 cd / mm ² .   2. The light guide unit according to claim 1, further comprising an incident end that receives excitation light emitted from the excitation light source, and an emission end that emits excitation light incident from the incident end to the light emitting unit. The vehicle headlamp described.   The vehicle headlamp according to claim 1, wherein the excitation light source emits excitation light having a peak wavelength in a wavelength range of 400 nm or more and 420 nm or less.   The vehicle headlamp according to claim 1 or 2, wherein the excitation light source emits excitation light having a peak wavelength in a wavelength range of 440 nm or more and 490 nm or less.   The vehicular headlamp according to any one of claims 1 to 4, wherein the vehicular headlamp is a traveling headlamp for an automobile.

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