JP7292119B2 - vehicle headlight - Google Patents

Description

The present invention relates to a vehicle headlamp.

In recent years, vehicle headlights use a laser light source such as a laser diode (LD) that provides high-brightness and high-output light, and irradiate the phosphor plate (wavelength conversion member) with the laser light emitted by this laser light source. Illumination light is obtained by doing so (see, for example, Patent Document 1 below).

Such vehicle headlights combine a laser light source that emits blue laser light and a phosphor plate that is excited by the blue laser light (excitation light) and emits wavelength-converted yellow light (fluorescence light). Therefore, it is possible to obtain white light (illumination light) by mixing the blue light and the yellow light.

In such a vehicle headlamp, as illumination light, a passing beam (low beam) forming a low beam light distribution pattern including a cut-off line at the upper end, and a high beam light distribution above the low beam light distribution pattern. A traveling beam (high beam) that forms a pattern is irradiated toward the front of the vehicle.

In a vehicle headlight, a plurality of irradiation areas corresponding to each light distribution pattern such as a light distribution pattern for low beam and a light distribution pattern for high beam are provided in the surface of the phosphor plate, and a laser is applied to each irradiation area. Irradiate while scanning light. Thereby, it is possible to form a plurality of different light distribution patterns.

JP 2016-134357 A

By the way, in the above-described conventional vehicle headlamp, one laser light source is used, and the laser light emitted from this laser light source is scanned within the plane of the phosphor plate. Therefore, in order to obtain illumination light with high brightness, it is necessary to increase the output of the laser light source.

On the other hand, when the output of the laser light source is increased, heat generation from the laser light source poses a problem. That is, the higher the output of a laser light source, the greater the amount of heat generated, so the current density required for laser oscillation increases as the temperature rises. In addition, in the case of a laser light source, when the temperature rises, the output is lowered and the life is shortened. Therefore, there is a natural limit to obtaining high-brightness illumination light by increasing the output of a single laser light source.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle headlamp capable of obtaining high-intensity illumination light using a plurality of laser light sources. and

In order to achieve the above object, the present invention provides the following means.
[1] a light source unit that emits excitation light;
A phosphor that emits wavelength-converted fluorescent light that is excited by irradiation with the excitation light,
A vehicle headlamp that emits illumination light obtained by mixing the excitation light and the fluorescent light toward the front of the vehicle,
The light source unit includes a first laser light source that emits a first laser beam;
a second laser light source that emits a second laser beam having a polarization direction different from that of the first laser beam;
a third laser light source that emits third laser light having a wavelength different from that of the first laser light and the second laser light;
a fourth laser light source that emits a fourth laser beam having a wavelength different from that of the first laser beam and the second laser beam and having a polarization direction different from that of the third laser beam; ,
a first polarizing beam splitter that transmits one of the first laser light and the second laser light and reflects the other to emit a combined first combined laser light;
a second polarizing beam splitter that transmits one of the third laser light and the fourth laser light and reflects the other to emit a second combined laser light that is combined;
A dichroic mirror that transmits one of the first combined laser light and the second combined laser light and reflects the other to emit the combined excitation light. headlights for vehicles.
[ 2 ] the peak wavelength of the first synthetic laser beam is in the range of 440 to 460 nm;
The peak wavelength of the third laser beam or the second synthetic laser beam is in the range of 470 to 480 nm,
A boundary wavelength between transmission and reflection of the dichroic mirror is between a peak wavelength of the first synthetic laser beam and a peak wavelength of the third laser beam or the second synthetic laser beam. The vehicle headlamp according to the above [1] .
[ 3 ] The vehicle headlamp according to [1] or [2] above, further comprising an excitation light scanning mechanism for scanning the excitation light within the surface of the phosphor.
[ 4 ] The vehicle headlamp according to any one of [1] to [ 3 ], further comprising a projection lens that projects the illumination light forward of the vehicle.

As described above, according to the present invention, it is possible to provide a vehicle headlamp capable of obtaining illumination light with high luminance using a plurality of laser light sources.

1 is a schematic diagram showing an example of a vehicle headlamp according to an embodiment of the present invention; FIG. FIG. 4 is a schematic diagram showing another example of the vehicle headlamp according to the embodiment of the present invention; FIG. 3 is a schematic diagram showing a configuration of a light source unit included in the vehicle headlamp shown in FIG. 1 or 2;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As one embodiment of the present invention, for example, a vehicle headlamp 1 shown in FIGS. 1, 2 and 3 will be described.
FIG. 1 is a schematic diagram showing an example of the vehicle headlamp 1. As shown in FIG. FIG. 2 is a schematic diagram showing another example of the vehicle headlamp 1. As shown in FIG. FIG. 3 is a schematic diagram showing the configuration of the light source unit 11 included in the vehicle headlamp 1 shown in FIG. 1 or 2. As shown in FIG.

A vehicle headlamp 1 of the present embodiment applies the present invention to a headlamp mounted on both front corners (in this embodiment, a left front corner) of a vehicle (not shown). It has a configuration as shown in FIG. 1 or 2, for example.

In the following description, unless otherwise specified, the terms "front", "rear", "left", "right", "upper", and "lower" are used when the vehicle headlamp 1 is viewed from the front (front of the vehicle). shall mean the respective directions when

Specifically, the vehicle headlamp 1 shown in FIG. A plate 12A, an excitation light scanning mechanism 13 that scans the excitation light BL irradiated toward the phosphor plate 12A, and a reflector that reflects the excitation light BL scanned by the excitation light scanning mechanism 13 toward the phosphor plate 12A. 14 and a projection lens 15 for projecting the illumination light WL toward the front of the vehicle B. As shown in FIG.

The light source unit 11 has a laser light source such as a laser diode (LD) that emits blue laser light (with an emission wavelength of approximately 450 nm) as excitation light BL. For the light source unit 11, a laser light source that emits ultraviolet laser light may be used as the excitation light BL.

The phosphor plate 12A is made of a plate-like wavelength conversion member containing yellow phosphor particles that are excited by the irradiation of the excitation light BL and emit yellow light as the fluorescence light YL. In this embodiment, as the wavelength conversion member, for example, one containing phosphor particles made of a composite (sintered body) of YAG into which an activator such as cerium Ce is introduced and alumina Al ₂ O ₃ is used. ing. In addition to the phosphor particles, the phosphor plate 12A may contain a diffusing agent in order to control the light distribution characteristics of the illumination light WL.

The excitation light scanning mechanism 13 consists of a MEMS (Micro-Electro-Mechanical Systems) mirror arranged in the optical path between the light source unit 11 and the phosphor plate 12A. The MEMS mirror is a movable mirror using MEMS technology, and controls the scanning direction and scanning speed of the excitation light BL that is two-dimensionally scanned within the surface of the phosphor plate 12A.

The reflector 14 consists of a mirror arranged in the optical path between the phosphor plate 12A and the excitation light scanning mechanism 13. As shown in FIG. The reflector 14 reflects the excitation light BL reflected by the MEMS mirror toward the back surface of the phosphor plate 12A.

In the vehicle headlamp 1 shown in FIG. 1, part of the excitation light (blue light) BL irradiated toward the back surface of the phosphor plate 12A is diffused and transmitted through the phosphor plate 12A, and the excitation light BL Illumination light (white light) obtained by mixing the excitation light BL and the fluorescence light YL while emitting fluorescence light (yellow light) YL by exciting the phosphor particles in the phosphor plate 12A by the irradiation of WL is emitted toward the front projection lens 15 .

On the other hand, the vehicle headlamp 1 shown in FIG. 2 includes a light source unit 11 that emits excitation light BL, and a reflective phosphor plate 12B that emits wavelength-converted fluorescent light YL that is excited by irradiation with the excitation light BL. , an excitation light scanning mechanism 13 that scans the excitation light BL irradiated toward the phosphor plate 12B, and a reflector 14 that reflects the excitation light BL scanned by the excitation light scanning mechanism 13 toward the phosphor plate 12B. , and a projection lens 15 for projecting the illumination light WL toward the front of the vehicle B.

That is, the vehicle headlamp 1 shown in FIG. 2 includes a reflective phosphor plate 12B instead of the transmissive phosphor plate 12A. Also, in the vehicle headlamp 1 shown in FIG. 2, the arrangement of the light source unit 11, the excitation light scanning mechanism 13 and the reflector 14 is changed according to the arrangement of the phosphor plate 12B. Other than that, it has basically the same configuration as the vehicle headlamp 1 shown in FIG.

The phosphor plate 12B has a configuration in which a reflector 16 is arranged on the back side of the wavelength conversion member that constitutes the phosphor plate 12A. The reflector 16 reflects the excitation light BL incident from the front side of the phosphor plate 12B and the fluorescence light YL excited within the phosphor plate 12B toward the front side of the phosphor plate 12B.

In the vehicle headlamp 1 shown in FIG. 2, part of the excitation light (blue light) BL emitted toward the front of the phosphor plate 12B is diffused and reflected by the phosphor plate 12B, and the excitation light The illumination light (white Light) WL is emitted toward the front projection lens 15 .

In the vehicle headlamp 1 shown in FIG. 1 or 2, the illumination light WL is a passing beam (low beam) that forms a low beam light distribution pattern including a cut-off line at the upper end, and a low beam light distribution pattern. A driving beam (high beam) that forms a high beam light distribution pattern above is irradiated toward the front of the vehicle.

In the vehicle headlamp 1, a plurality of irradiation areas corresponding to each light distribution pattern such as a light distribution pattern for low beam and a light distribution pattern for high beam are provided in the surface of the phosphor plate, and each irradiation area A laser beam is irradiated while scanning. This makes it possible to form a plurality of different light distribution patterns.

By the way, the vehicle headlamp 1 of this embodiment includes a light source unit 11 using a plurality of (four in this embodiment) laser light sources 2A to 2D shown in FIG. Note that FIG. 3 omits the configuration of the vehicle headlamp 1 shown in FIG. 1 or 2 except for the light source unit 11 and the phosphor plates 12A and 12B.

Specifically, the light source unit 11 includes a first laser light source 2A that emits a first laser beam L1, a second laser light source 2B that emits a second laser beam L2, and a third laser beam L3. and a fourth laser light source 2D for emitting a fourth laser light L4.

Further, the light source unit 11 transmits either one of the first laser beam L1 and the second laser beam L2 (the first laser beam L1 in the present embodiment) and the other (the second laser beam L1 in the present embodiment). a first polarizing beam splitter 3A that emits a first combined laser beam L12 synthesized by reflecting the laser beams L2) of 2), and any one of the third laser beam L3 and the fourth laser beam L4. One (the third laser beam L3 in this embodiment) is transmitted and the other (the fourth laser beam L4 in this embodiment) is reflected to emit a second combined laser beam L34. and a second polarizing beam splitter 3B.

Further, the light source unit 11 transmits either one of the first combined laser beam L12 and the second combined laser beam L34 (in this embodiment, the second combined laser beam L34), and the other (this embodiment). In the embodiment, a dichroic mirror 4 is provided for emitting the combined excitation light BL by reflecting the first combined laser light L12).

The light source unit 11 also includes a first mirror 5A that reflects the second laser beam L2 toward the first polarizing beam splitter 3A, and a fourth laser beam L4 toward the second polarizing beam splitter 3B. A reflecting second mirror 5B and a third mirror 5C reflecting the first combined laser beam L12 toward the dichroic mirror 4 are provided.

In the light source unit 11, in order to implement such a configuration, the first laser beam L1 and the second laser beam L2 are in the same wavelength range. Also, the first laser beam L1 and the second laser beam L2 have different polarization directions with respect to the first polarization beam splitter 3A.

On the other hand, the third laser light L3 and the fourth laser light L4 are in the same wavelength range, and are in a different wavelength range from the first laser light L1 and the second laser light L2. Also, the third laser beam L3 and the fourth laser beam L4 have different polarization directions with respect to the second polarization beam splitter 3B.

In this embodiment, the peak wavelength of the first combined laser beam L12 (the first laser beam L1 and the second laser beam L2) is in the range of 440-460 nm. On the other hand, the peak wavelength of the second combined laser beam L34 (the third laser beam L3 and the fourth laser beam L4) is in the range of 470-480 nm. The boundary wavelength between transmission and reflection of the dichroic mirror 3 is between the peak wavelength of the first combined laser beam L12 and the peak wavelength of the second combined laser beam L34 (460-470 nm).

Each of the first to fourth laser beams L1 to L4 has a wavelength range that excites the yellow phosphor particles of the phosphor plate 12A to emit fluorescence light (yellow light) YL as the excitation light BL. It is a wavelength range in which illumination light (white light) WL is obtained by mixing light BL and fluorescent light YL.

As a result, in the light source unit 11 of the present embodiment, the excitation light BL synthesized from the first to fourth laser beams L1 to L4 emitted from the first to fourth laser light sources 1A to 1D is emitted from the phosphor plate 12A and the phosphor plate 12A. 12B can be emitted. Also, by synthesizing the first to fourth laser beams L1 to L4, it is possible to obtain high-power excitation light BL.

Therefore, in the vehicle headlamp 1 of the present embodiment, it is possible to obtain illumination light WL with high brightness using the above-described high-output excitation light BL. In addition, in the vehicle headlamp 1 of the present embodiment, high-power excitation light BL can be obtained without increasing the output of each laser light source 1A to 1D, so that each laser light source 1A to 1D becomes hot. It is also possible to extend the life of each of the laser light sources 1A to 1D while suppressing the Furthermore, in the vehicle headlamp 1 of the present embodiment, it is possible to obtain high-power pumping light BL using relatively inexpensive and compact laser light sources 1A to 1D.

Further, in the vehicle headlamp 1 of the present embodiment, the laser light sources 1A to 1D are driven by a common driving device 20 as shown in FIG. The drive device 20 is connected to the storage device 30 . The storage device 30 stores a table of current value-output characteristics of the excitation light BL after combining the first to fourth laser beams L1 to L4.

The driving device 20 controls the current value of each of the laser light sources 1A to 1D while referring to the current value-output characteristic table in the storage device 30 so that the excitation light BL has a desired output. Each laser light source 1A-1D is driven by a single current value. This eliminates the need for multiple driving devices for separately controlling the light sources 1A-1D.

Even if the first and second laser light sources 1A and 1B and the third and fourth laser light sources 1C and 1D having different wavelength ranges described above have different current value-output characteristics, the same phosphor It is a light source in a wavelength range capable of exciting the yellow phosphor particles of the plate 12A. Therefore, fluctuations in the spectrum of the synthesized excitation light BL caused by fluctuations in the output ratio of the light sources 1A to 1D do not cause any particular problems in the vehicle headlamp 1. FIG.

It should be noted that the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.
For example, the light source unit 11 has a configuration including four laser light sources 2A to 2D, but it is also possible to have a configuration in which the fourth laser light source 2D and the second mirror 5B are omitted. In this case, it is possible to emit the excitation light BL, which is a combination of the first to third laser beams L1 to L3 emitted from the three laser light sources 2A, 2B, 2C, toward the phosphor plates 12A, 12B. .

Although not shown, the vehicle headlamp 1 can be configured to dissipate the heat generated by the laser light sources 1A to 1D to the outside using, for example, a heat sink or a cooling fan. be.

Further, the vehicle headlamp 1 may be configured to form a light distribution pattern for drawing a road surface, etc. separately from the light distribution pattern for low beam and the light distribution pattern for high beam described above. Examples of the road surface drawing light distribution pattern include characters, symbols, and graphics.

DESCRIPTION OF SYMBOLS 1... Vehicle headlamp 2A... 1st laser light source 2B... 2nd laser light source 2C... 3rd laser light source 2D... 4th laser light source 3A... 1st polarization beam splitter 3B... 2nd polarization beam Splitter 4 Dichroic mirror 5A First mirror 5B Second mirror 5C Third mirror 11 Light source unit 12A, 12B Phosphor plate (wavelength conversion member) 13 Excitation light scanning mechanism 14 Reflector 15 Projection lens BL... Excitation light YL... Fluorescence light WL... Illumination light L1... First laser light L2... Second laser light L3... Third laser light L4... Fourth laser light L12... First synthetic laser light L34: second synthetic laser light

Claims (4)

a light source unit that emits excitation light;
A phosphor that emits wavelength-converted fluorescent light that is excited by irradiation with the excitation light,
A vehicle headlamp that emits illumination light obtained by mixing the excitation light and the fluorescent light toward the front of the vehicle,
The light source unit includes a first laser light source that emits a first laser beam;
a second laser light source that emits a second laser beam having a polarization direction different from that of the first laser beam;
a third laser light source that emits third laser light having a wavelength different from that of the first laser light and the second laser light;
a fourth laser light source that emits a fourth laser beam having a wavelength different from that of the first laser beam and the second laser beam and having a polarization direction different from that of the third laser beam; ,
a first polarizing beam splitter that transmits one of the first laser light and the second laser light and reflects the other to emit a combined first combined laser light;
a second polarizing beam splitter that transmits one of the third laser light and the fourth laser light and reflects the other to emit a second combined laser light that is combined;
A dichroic mirror that transmits one of the first combined laser light and the second combined laser light and reflects the other to emit the combined excitation light. headlights for vehicles. The peak wavelength of the first synthetic laser light is in the range of 440 to 460 nm,
The peak wavelength of the third laser beam or the second synthetic laser beam is in the range of 470 to 480 nm,
A boundary wavelength between transmission and reflection of the dichroic mirror is between a peak wavelength of the first synthetic laser beam and a peak wavelength of the third laser beam or the second synthetic laser beam. The vehicle headlamp according to claim 1 . 3. The vehicle headlamp according to claim 1, further comprising an excitation light scanning mechanism for scanning the excitation light within the plane of the phosphor. The vehicle headlamp according to any one of claims 1 to 3 , further comprising a projection lens that projects the illumination light forward of the vehicle.

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