EP2985519B1

EP2985519B1 - Vehicle lamp fitting

Info

Publication number: EP2985519B1
Application number: EP14780115.3A
Authority: EP
Inventors: Toshiaki Tsuda; Takeshi Masuda
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 2013-04-04
Filing date: 2014-03-20
Publication date: 2018-06-13
Anticipated expiration: 2034-03-20
Also published as: EP3279553B1; WO2014162683A1; CN105074328B; EP2985519A1; EP3279553A1; JPWO2014162683A1; CN105074328A; EP2985519A4

Description

The present invention relates to an automotive lamp, and more particularly to an automotive lamp used for a vehicle such as an automobile.
Document US 2012/0299476 A1 describes a vehicle signal light with light sources emitting in three different colours.
Patent Document 1 discloses an automotive lamp comprised of a semiconductor light source, a mirror, which reflects the light, emitted from the semiconductor light source, around a vehicle, and a scanning actuator for turnably reciprocating the mirror. In this automotive lamp, the scanning actuator drives the mirror at high speed and scans the light reflected by the mirror in a predetermined illumination range around the vehicle, thereby forming a predetermined light distribution pattern in a frontward direction of the vehicle. Hereafter, such an optical system as this will be appropriately referred to as a "scanning optical system" also. Also, in this automotive lamp, a red LED, a green LED and a blue LED are combined and used as the light source.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2010-36835 .
The laser light source can emit light excellent in directivity and convergence in comparison with the LED. Accordingly, the laser light source can help improve the light availability in the automotive light more than the LED. Since the light availability of the automotive lamp can be improved, the laser light can be preferably employed for an automotive lamp equipped with the above-described scanning optical system whose light availability is more likely to be reduced. In the light of this, through diligent research activities on the automotive lamp using the laser light source, the inventors of the present invention have found out that there is room for improvement in the performance of the conventional automotive lamp when the laser light source is used for the conventional automotive lamp.
Also, the inventors have found out that when the LED is replaced by the laser light source in the above-described conventional automotive lamp, namely when white light is formed by combining the red, green and blue laser lights, an improvement in the color rendering properties is desired.
The present invention has been made in view of the foregoing circumstances, and one of purposes thereof is to provide a technology that helps improve the performance of an automotive lamp equipped with a laser light source.
Another purpose thereof is to provide a technology that helps improve the color rendering properties of the automotive lamp equipped with the laser light source.
In order to resolve the above-described problems, one embodiment of the present embodiment relates to an automotive lamp. The automotive lamp includes: a first light source that emits a first laser light having a peak wavelength in a wavelength region of 450 nm to 475 nm (both inclusive); a second light source that emits a second laser light having a peak wavelength in a wavelength region of 525 nm to 555 nm (both inclusive), wherein an interval between the peak wavelength of the first laser light and the peak wavelength of the second laser light is greater than or equal to 65 nm and less than or equal to 95 nm; a third light source that emits a third laser light having a peak wavelength in a wavelength region of 605 nm to 620 nm (both inclusive), wherein an interval between the peak wavelength of the second laser light and the peak wavelength of the third laser light is greater than or equal to 60 nm and less than 80 nm, and an interval between the peak wavelength of the first laser light and the peak wavelength of the third laser light is less than 170 nm; and a light condensing unit that collects the first to third laser lights so as to generate a white laser light. By employing this embodiment, the performance of the automotive lamp equipped with the laser light sources can be improved.
In the above-described embodiment, the third laser light may have a peak wavelength in a wavelength region of 610 nm to 620 nm (both inclusive). In any of the above-described embodiments, the first laser light may have a peak wavelength in a wavelength region of 450 nm to 470 nm (both inclusive). By employing these embodiments, the performance of the automotive lamp equipped with the laser light sources can be further improved. Optional combinations of the aforementioned constituting elements, and implementations of the invention in the form of methods, apparatuses, systems and so forth may also be practiced as additional modes of the present invention.
Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:

FIG. 1 is a vertical cross-sectional view schematically showing a structure of an automotive lamp according to a first embodiment;
FIG. 2 is a side view schematically showing a structure of a light source unit;
FIG. 3 is a schematic perspective view of a scanning unit as observed from a front side of a lamp;
FIG. 4 shows an exemplary light distribution pattern formed by an automotive lamp according to an embodiment;
FIG. 5A is a graph showing the spectral distribution of the conventional white LED;
FIG. 5B is a graph showing the spectral distribution of the RGB laser light source;
FIG. 5C is a table showing the color rendering indexes Ra and R9 and the theoretical efficiency of each of RGB laser light source and white LED;
FIG. 6 is a table showing calculation results of average color rendering indexes Ra;
FIG. 7 is a table showing calculation results of average color rendering indexes Ra;
FIG. 8 is a table showing calculation results of average color rendering indexes Ra;
FIG. 9 is a table showing calculation results of special color rendering indexes R9;
FIG. 10 is a table showing calculation results of special color rendering indexes R9;
FIG. 11 is a table showing calculation results of theoretical efficiencies;
FIG. 12 is a table showing calculation results of theoretical efficiencies.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the accompanying drawings.
The same or equivalent constituents, members, or processes illustrated in each drawing will be denoted with the same reference numerals, and the repeated description thereof will be omitted as appropriate.
The preferred embodiments do not intend to limit the scope of the invention but exemplify the invention. All of the features and the combinations thereof described in the embodiments are not necessarily essential to the invention.
FIG. 1 is a vertical cross-sectional view schematically showing a structure of an automotive lamp according to an embodiment. In FIG. 1, a light source unit 100 is shown in a state where the interior thereof is seen through. Also, permanent magnets 312 and 314 of a scanning unit 300 are omitted in FIG. 1. The automotive lamp according to the present embodiment is, for instance, an automotive headlamp apparatus that has a pair of headlamp units placed in left- and right-side front parts of a vehicle. Since the pair of headlamp units are of practically identical structure to each other, FIG. 1 shows the structure of either one of the left and right headlamp units, as an automotive lamp 1. Note that the structure of the automotive lamp 1 described below is exemplary and is not limited to the structure shown and explained below.
The automotive lamp 1 includes a lamp body 2, having an opening on a frontward side of a vehicle, and a transparent cover 4, which covers the opening of the lamp body 2. The transparent cover 4 is formed of resin or glass, having translucency, for instance. A lamp chamber 3, which is formed by the lamp body 2 and the transparent cover 4, contains a supporting plate 6, a light source unit 100, a scanning unit 300, and a control unit 400.
The light source unit 100 and the scanning unit 300 are supported by the supporting plate 6 at predetermined positions in the lamp chamber 3. The supporting plate 6 is connected to the lamp body 2 by aiming screws 8 at corners of the supporting plate 6. The light source unit 100 has a first light source 102, a second light source 104, a third light source 106, a heatsink 110, a light condensing unit 200, and so forth. The light source unit 100 is fixed on a front surface of the supporting plate 6 such that the heatsink 110 is in contact with the supporting plate 6. A detailed description will be given later of the internal structure of the light source unit 100.
The scanning unit 300 has a reflector 318. The structure of the scanning unit 300 will be discussed later in detail. The scanning unit 300 is positioned relative to the light source unit 100 in a predetermined manner such that laser light emitted from the light source unit 100 is reflected in a frontward direction of the lamp. And the scanning unit 300 is secured to a protrusion 10 that protrudes on a frontward side of the lamp from the front surface of the supporting plate 6. The protrusion 10 has a pivot mechanism 10a, and the scanning unit 300 is supported by the protrusion 10 via the pivot mechanism 10a. Also, the protrusion 10 has a supporting actuator 10b, having a rod and a motor by which to elongate and contract this rod in the longitudinal directions of the lamp. The tip of the rod is connected to the scanning unit 300. The protrusion 10 enables the scanning unit 300 to make a swing motion by having the rod elongate and contract with the pivot mechanism 10a functioning as a shaft. This can adjust the inclination angle (pitch angle) of the scanning unit 300 in the vertical direction (initial aiming adjustment and the like). The supporting actuator 10b is connected to the control unit 400.
The control unit 400 includes a lamp ECU, a ROM, a RAM and so forth. Here, the lamp ECU appropriately and selectively executes a control program and generates various control signals. The ROM stores various control programs. The RAM is used for data storage and used as a work area for the programs executed by the lamp ECU. The control unit 400 controls the drive of the supporting actuator 10b, the drive of a scanning actuator described later, the turning on and off of the first light source 102 to the third light source 106, and so forth. The control unit 400 is secured to the lamp body 2 such that the control unit 400 is located behind the supporting plate 6 toward the rear end of the lamp. The position where the control unit 400 is provided is not particular limited to this position.
The automotive lamp 1 is configured such that the light axis of the automotive lamp 1 is adjustable in the horizontal and vertical directions. More specifically, adjusting the position (posture) of the supporting plate 6 by rotating the aiming screws 8 allows the light axis thereof to be adjusted in the horizontal and vertical directions. An extension member 12, having an opening that allows the light reflected by the scanning unit 300 to travel toward a front area of the lamp, is provided in a frontward side of the light source unit 100 and the scanning unit 300 in the lamp chamber 3. A detailed description is given hereunder of the structures of the light source unit and the scanning unit that constitute the automotive lamp 1.

(Light source unit)

FIG. 2 is a side view schematically showing a structure of the light source unit. Note that FIG. 2 is a transparent view showing the interior of the light source unit 100. The light source unit 100 has a first light source 102, a second light source 104, a third light source 106, a heatsink 110, a first lens 112, a second lens 114, a third lens 116, a light transmission part 120, a light condensing unit 200, and other components.
The first light source 102 emits a first laser light B having a peak wavelength in an approximate wavelength region of blue light. The second light source 104 emits a second laser light G having a peak wavelength in an approximate wavelength region of green light. The third light source 106 emits a third laser light O having a peak wavelength in an approximate wavelength region of orange light. A detailed description will be given later of the peak wavelengths of the first laser light B to the third laser light O. The first light source 102 to the third light source 106 are each constituted by a laser diode, for instance, and are mounted on a common substrate 109. Each light source may be constituted by a laser device other than the laser diode.
The first light source 102, the second light source 104 and the third light source 106 are arranged such that their respective laser light emission surfaces face a front area of the lamp and such that the substrate 109 faces a rear area of the lamp. Also, the first to third light sources 102, 104 and 106 are mounted on a surface of the heatsink 110 that faces a front area of the lamp. The heatsink 110 is formed of a material, having a high thermal conductivity, such as aluminum, for the purpose of efficiently recovering the heat produced by each light source. A rear-side surface of the heatsink 110 is in contact with the supporting plate 6 (see FIG. 1). The heat produced by each light source is radiated through the substrate 109, the heatsink 110 and the supporting plate 6.
The first lens 112, the second lens 114 and the third lens 116 are each a collimator lens, for instance. The first lens 112 is provided on a light path of the first laser light B between the first light source 102 and the light condensing unit 200, and converts the first laser light B, emitted from the first light source 102 toward the light condensing unit 200, into parallel light. The second lens 114 is provided on a light path of the second laser light G between the second light source 104 and the light condensing unit 200, and converts the second laser light G, emitted from the second light source 104 toward the light condensing unit 200, into parallel light. The third lens 116 is provided on a light path of the third laser light O between the third light source 106 and the light condensing unit 200, and converts the third laser light O, emitted from the third light source 106 toward the light condensing unit 200, into parallel light.
The light transmission part 120 is fitted to an opening 101 formed in a housing of the light source unit 100. A white laser light W described later passes through the light transmission part 120 from the light condensing unit 200 and travels toward the scanning unit 300.
The light condensing unit 200 (polarizing unit) collects the first laser light B, the second laser light G and the third laser light O so as to generate the white laser light W. The light condensing unit 200 has a first dichroic mirror 202, a second dichroic mirror 204 and a third dichroic mirror 206.
The first dichroic mirror 202 is a mirror that reflects at least the first laser light B, and is arranged such it reflects the first laser light B, which has passed through the first lens 112, toward the light transmission part 120. The second dichroic mirror 204 is a mirror that reflects at least the second laser light G and transmits the first laser light B, and is arranged such it reflects the second laser light G, which has passed through the second lens 114, toward the light transmission part 120. The third dichroic mirror 206 is a mirror that reflects at least the third laser light O and transmits the first laser light B and the second laser light G, and is arranged such it reflects the third laser light O, which has passed through the third lens 116, toward the light transmission part 120.
A mutual positional relation among the dichroic mirrors 202 to 206 is determined such that the light paths of the laser lights reflected by the dichroic mirrors 202 to 206 are parallel to each other and such that their respective laser lights are collected and the thus collected light transmits the light transmission part 120. In the present embodiment, the first dichroic mirror 202 to the third dichroic mirror 206 are arranged such that the areas where the laser lights strike on the respective dichroic mirrors, namely the reflecting points of laser lights, are aligned on a same line.
The first laser light B emitted from the first light source 102 is reflected by the first dichroic mirror 202 toward the second dichroic mirror 204. The second laser light G emitted from the second light source 104 is reflected by the second dichroic mirror 204 toward the third dichroic mirror 206, and the thus reflected light is simultaneously superposed on the first laser light B that has transmitted the second dichroic mirror 204. The third laser light O emitted from the third light source 106 is reflected by the third dichroic mirror 206 toward the light transmission part 120, and the thus reflected light is superposed on the first laser light B and the second laser light G that have transmitted the third dichroic mirror 206. As a result, the white laser light W is formed. The white laser light W passes through the light transmission part 120 and travels toward the scanning unit 300.

(Scanning unit)

FIG. 3 is a schematic perspective view of a scanning unit as observed from a front side of the lamp. The scanning unit 300 is a mechanism used to scan the laser lights, emitted from the first light source 102 to the third light source 106, and form a predetermined light distribution pattern (see FIG. 4). The scanning unit 300 includes a base 302, a first rotating body 304, a second rotating body 306, first torsion bars 308, second torsion bars 310, permanent magnets 312 and 314, a terminal part 316, a reflector 318, and so forth. The base 302 is a frame body having an opening 302a in the center, and is secured to the tip of the protrusion 10 (see FIG. 1) such that the base 302 is tilted in the longitudinal directions of the lamp. The terminal part 316 is provided in a predetermined position of the base 302. The first rotating body 304 is arranged in the opening 302a. The first rotating body 304 is a frame body having an opening 304a in the center, and is turnably supported by the first torsion bars 308, which extend, from a rear lower side to a frontal upper side of the lamp, laterally (in the vehicle width direction) in relation to the base 302.
The second rotating body 306 is arranged in the opening 304a of the first rotating body 304. The second rotating body 306 is a rectangular plate, and is turnably supported by the second torsion bars 310, which extend in the vehicle width direction, vertically in relation to the first rotating body 304. When the first rotating body 304 is turned laterally with the first torsion bars 308 as a turning shaft, the second rotating body 306 is turned laterally together with the first rotating body 304. The reflector 318 is provided on the surface of the second rotating body 306 by use of a plating, vapor deposition or like method.
A pair of permanent magnets 312 are provided on the base 302 in a position orthogonal to the direction along which the first torsion bars 308 extend. The permanent magnets 312 form a magnetic field running orthogonal to the first torsion bars 308. A first coil (not shown) is wired in the first rotating body 304, and the first coil is connected to the control unit 400 via the terminal part 316 (see FIG. 1). Also, a pair of permanent magnets 314 are provided on the base 302 in a position orthogonal to the direction along which the second torsion bars 310 extend. The permanent magnets 314 form a magnetic field running orthogonal to the second torsion bars 310. A second coil (not shown) is wired in the second rotating body 306, and the second coil is connected to the control unit 400 via the terminal part 316.
The first coil and the permanent magnets 312, and the second coil and the permanent magnets 314 constitute a scanning actuator. The drive of the scanning actuator is controlled by the control unit 400. The control unit 400 controls the amount and the direction of electric current flowing through the first coil and the second coil. Controlling the amount and the direction of electric current flowing therethrough enables the first rotating body 304 and the second rotating body 306 to turnably reciprocate from side to side (laterally) and enables the second rotating body 306 to turnably reciprocate vertically independently. As a result, the reflector 318 makes turnably reciprocating movements in vertical and lateral directions.
The white laser light W emitted from the light source unit 100 is reflected, by the reflector 318, in a frontward direction of the lamp. Then the scanning unit 300 scans a front area of the vehicle using the white laser light W by turnably reciprocating the reflector 318. For example, the scanning unit 300 turns the reflector 318 over a scanning range that is wider than a region where the light distribution pattern is formed. Then the control unit 400 turns on the first light source 102 to the third light source 106 when the turning position of the reflector 318 is in a position corresponding to the region where the light distribution pattern is formed. Thereby, the white laser light W is distributed over the region where the light distribution pattern is formed and, as a result, a predetermined light distribution pattern is formed in the front area of the vehicle.

(Shape of light distribution pattern)

FIG. 4 shows an exemplary light distribution pattern formed by the automotive lamp according to the first embodiment. FIG. 4 shows a visible light distribution pattern formed on a vertical screen placed at a predetermined position in front of the lamp, for example, at a point 25 meters ahead of the lamp. The scan tracks of the laser light are shown schematically using broken lines and solid line.
The scanning unit 300 can scan a rectangular scan area SA, which extends in the vehicle width direction, with the laser light. When a scanning position of laser light by the scanning unit 300 is within a low beam distribution pattern Lo, the control unit 400 has each of the first light source 102 to the third light source 106 emit the laser light. When the scanning position thereof is outside the low beam distribution pattern Lo, the control unit 400 stops the emission of the laser light from each of the first light source 102 to the third light source 106. This forms the low beam distribution pattern Lo having a cutoff line CL1 on the side of an oncoming traffic lane, a cutoff line CL2 on the side of a driver's own lane and a sloping cutoff line CL3. Note that the automotive lamp 1 can also form other light distribution patterns such as a high beam distribution pattern.

(The peak wavelength of each light source)

A detailed description is now given of the peak wavelength of laser light emitted from each of the first light source 102 to the third light source 106. FIG. 5A is a graph showing the spectral distribution of the conventional white LED. FIG. 5B is a graph showing the spectral distribution of the RGB laser light source. FIG. 5C is a table showing the color rendering indexes Ra and R9 and the theoretical efficiency of each of RGB laser light source and white LED. FIGS. 5A and 5B are graphs where the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the relative irradiance. For example, the RGB laser light source is a light source emitting the white laser light such that a red laser light, whose peak wavelength is 639 nm, a green laser light, whose peak wavelength is 532 nm, and a blue laser light, whose peak wavelength is 465 nm, are combined together.
As shown in FIG. 5A, the white light emitted from the white LED indicates a high irradiance in a wavelength region wider than that of the RGB laser light source. On the other hand, as shown in FIG. 5B, the white light emitted from the RGB laser light source has peak wavelengths, each having an extremely narrow bandwidth (half bandwidth), in a wavelength region of the blue light, in a wavelength region of the green light and in a wavelength region of the red light, respectively.
An average color rendering index Ra, a special color rendering index R9 and a theoretical efficiency (Im/W) of light irradiated from each of the white LED and the RGB laser light source having such spectral distribution characteristics are those indicated in FIG. 5C. The values indicated in FIG. 5C are values derived such that the chromaticity (x, y) of the respective irradiation lights and the color temperatures thereof are adjusted to the chromaticities and the color temperatures generally required of the automotive lamp. The aforementioned "theoretical efficiency" as meant here indicates the luminous efficacy when all of the energy inputted to the light source is outputted as visible light. As shown in FIG. 5C, the RGB light source indicates values lower than those of the white LED in terms of all of Ra, R9 and the theoretical efficiency.
In contrast to this, the automotive lamp 1 according to the present embodiment has the following features regarding the peak wavelengths of the first laser light B to the third laser light O, respectively. Specifically, the first laser light B emitted by the first light source 102 has a peak wavelength in the wavelength region of 450 nm to 475 nm (both inclusive). Also, the second laser light G emitted by the second light source 104 has a peak wavelength in the wavelength region of 525 nm to 555 nm (both inclusive). Also, the third laser light O emitted by the third light source 106 has a peak wavelength in the wavelength region of 605 nm to 620 nm (both inclusive).
The interval between the peak wavelength of the first laser light B and the peak wavelength of the second laser light G is greater than or equal to 65 nm and less than or equal to 95 nm. Also, the interval between the peak wavelength of the second laser light G and the peak wavelength of the third laser light O is greater than or equal to 60 nm and less than 80 nm. Also, the interval between the peak wavelength of the first laser light B and the peak wavelength of the third laser light O is less than 170 nm.
If the first laser light B to the third laser light O satisfy the above-described conditions for the peak wavelengths, the automotive lamp 1 can irradiate the light that satisfies the Ra (e.g., Ra=60) generally required of the automotive lamp. As a result, the preferred laser light source can be provided as the light source of the automotive lamp.
It is preferable that the third laser light O has a peak wavelength in the wavelength region of 610 nm to 620 nm (both inclusive). Setting the peak wavelength of the third laser light O in the wavelength region of 610 nm to 620 nm (both inclusive) allows the R9 of the irradiation light to be improved. R9 is used for evaluation of red color. It is required of the automotive lamp that the red color of tail lamps and the like of other vehicles be more accurately expressed. For this purpose, R9 is just as important characteristic as Ra for the automotive lamp. Thus, improving the R9 of the irradiation light enables the performance of the automotive lamp to be further raised.
Also, it is preferable that the first laser light B has a peak wavelength in the wavelength region of 450 nm to 470 nm (both inclusive). Setting the peak wavelength of the first laser light B in the wavelength region of 450 nm to 470 nm (both inclusive) allows an excellent theoretical efficiency to be given more reliably to the automotive lamp. This can, for example, improve the luminance of the irradiation light and reduce the power consumed by the automotive lamp. Thus, the performance of the automotive can be further improved.

(Calculation of average color rendering index Ra)

Ra was calculated for irradiation light of the automotive lamp. In the course of calculating the Ra, the irradiation light of the automotive lamp 1 was adjusted such that the chromaticity (x, y) lies in a range where 0.34≤x≤0.36 and 0.34≤y≤0.36 and such that the color temperature (K) ranges from 4500 to 5500 (both inclusive). Ra can be calculated by following a method defined in the Japanese Industrial Standards JIS Z 8726. In the present embodiment, Ra=60, which is generally required of the automotive lamp, is set as a threshold value. When Ra is greater than or equal to 60, the evaluation was made as "A"; when Ra is less than 60, the evaluation was made as "B". The results are shown in FIG. 6 to FIG. 8.
FIGS. 6, 7 and 8 are tables showing the calculation results of average color rendering indexes Ra. In the tables shown in FIGS. 6, 7 and 8, "2nd-1st" means the interval between the peak wavelengths of the second laser light G and the first laser light B. Similarly, "3rd-2nd" means the interval between the peak wavelengths of the third laser light O and the second laser light G; "3rd-1st" means the interval between the peak wavelengths of the third laser light O and the first laser light B. Also, the hatched cells under "2nd-1st", "3rd-2nd" and "3rd-1st" of each of FIGS. 6, 7 and 8 indicate that the intervals therebetween regarding "2nd-1st", "3rd-2nd", "3rd-1st" do not meet the above-described conditions. Similarly, the hatched cells under "Ra" of each of FIGS. 6, 7 and 8 regarding "Ra" indicate that the average color rendering indexes Ra are less than 60; the hatched cells under "determination (evaluation)" indicate that the evaluations are "B".
As shown in FIGS. 6, 7 and 8, it was verified that Ra of the irradiation light of the automotive lamp is greater than or equal to 60 and therefore an excellent Ra is obtained under the following conditions. That is, Ra is greater than or equal to 60 when the first laser light B has a peak wavelength ranging from 450 nm to 475 nm (both inclusive), the second laser light G has a peak wavelength ranging from 525 nm to 555 nm (both inclusive), the third laser light O has a peak wavelength ranging from 605 nm to 620 nm (both inclusive), and when the interval between the peak wavelengths of the first laser light B and the second laser light G is greater than or equal to 65 nm and less than or equal to 95 nm, the interval between the peak wavelengths of the second laser light G and the third laser light O is greater than or equal to 60 nm and less than 80 nm, and the interval between the peak wavelengths of the first laser light B and the third laser light O is less than 170 nm.

(Calculation of special color rendering index R9)

R9 was calculated for irradiation light, of the automotive lamp, whose determination was "A" in the above-described calculation of Ra. The chromaticity and the color temperature were set similarly to the calculation of Ra. R9 can be calculated by following the method defined in the Japanese Industrial Standards JIS Z 8726. In the present embodiment, R9=-37.4 of white LED (see FIG. 5C) is set as a threshold value. When R9 is greater than or equal to -37.4, the evaluation was made as "AA"; when R9 is less than -37.4, the evaluation was made as "A". The results are shown in FIGS. 9 and 10.
FIGS. 9 and 10 are tables showing the calculation results of special color rendering indexes R9. In the tables shown in FIGS. 9 and 10, "2nd-1st", "3rd-2nd" and "3rd-1st" mean ones similar to FIG. 6 to FIG. 8, respectively. In FIGS. 9 and 10, the irradiation lights whose evaluatins of R9 are "A" are indicated as hatched cells under the columns of "third light source", "R9" and "evaluation", respectively.
As shown in FIGS. 9 and 10, it was verified that R9 of the irradiation light of the automotive vehicle is greater than or equal to -37.4 and therefore an excellent R9 is obtained when the third laser light O has a peak wavelength ranging from 610 nm to 620 nm (both inclusive).

(Calculation of theoretical efficiency)

Then, the theoretical efficiency (Im/W) was calculated for irradiation light, of the automotive lamp, whose determination was "AA" in the above-described calculation of R9. The chromaticity and the color temperature were set similarly to the calculation of Ra. The theoretical efficiency η_theo can be calculated based on the following Equation. In the present embodiment, [theoretical efficiency]=330, which is equal to the theoretical efficiency of white LED, is set as a threshold value. When the theoretical efficiency is greater than or equal to 330, the evaluation was made as "AAA"; when the theoretical efficiency is less than 330, the evaluation was made as "AA". The results are shown in FIGS. 11 and 12. $T h e o r e t i c a l e f f i c i e n c y η_{theo} = \frac{k_{m} \times \int_{λ = 380 nm}^{780 nm} E_{e} (λ) \times V (λ) \times dλ}{\int_{λ = 380 nm}^{780 nm} E_{e} (λ) \times dλ}$

E_e(λ): Spectral distribution of radiant flux
V(λ): Spectral luminous efficacy
K_m(=683 [Im/W]): luminous efficacy.

FIGS. 11 and 12 are tables showing the calculation results of theoretical efficiencies. In the tables shown in FIGS. 11 and 12, "2nd-1st", "3rd-2nd" and "3rd-1st" mean ones similar to FIG. 6 to FIG. 8, respectively. In FIGS. 11 and 12, the irradiation lights whose evaluations of theoretical efficiency are "AA" are indicated as hatched cells under the columns of "first light source", "theoretical efficiency" and "evaluation", respectively.
As shown in FIGS. 11 and 12, it was verified that the theoretical efficiency of the irradiation light of the automotive lamp is greater than or equal to 330 and therefore an excellent theoretical efficiency is obtained when the first laser light B has a peak wavelength ranging from 450 nm to 470 nm (both inclusive).
As described above, the automotive lamp 1 according to the present embodiment includes the first light source 102 that emits the first laser light B having a peak wavelength in the wavelength region of 450 nm to 475 nm (both inclusive), the second light source 104 that emits the second laser light G having a peak wavelength in the wavelength region of 525 nm to 555 nm (both inclusive), the interval between the peak wavelength of the first laser light B and the peak wavelength of the second laser light G being greater than or equal to 65 nm and less than or equal to 95 nm, the third light source 106 that emits the third laser light O having a peak wavelength in the wavelength region of 605 nm to 620 nm (both inclusive), the interval between the peak wavelength of the second laser light G and the peak wavelength of the third laser light O being greater than or equal to 60 nm and less than 80 nm, and the interval between the peak wavelength of the first laser light B and the peak wavelength of the third laser light O being less than 170 nm, and the light condensing unit 200 that collects the first to third laser lights so as to generate a white laser light. As result, the color rendering properties of the automotive lamp equipped with the laser light sources can be improved. Thus, the performance of the automotive lamp 1 can be improved. Also, installing the automotive lamp equipped with such laser light sources in the vehicle can improve the light availability of the automotive lamp while the drop in the visibility of the driver is being suppressed or the visibility thereof is being improved.
The present invention is not limited to the above-described embodiments only, and those resulting from any appropriate combination of and/or replacement with a component or components of any of the embodiments are included in the present embodiment. Also, it is understood by those skilled in the art that various modifications such as changes in design may be added to each of the embodiments based on their knowledge and newly combined embodiments or embodiments added with such modifications are also within the scope of the present invention.
In the above-described embodiments, the scanning unit 300 can be configured by a galvanometer mirror, an MEMS mirror type, a polygon mirror type and so forth. Also, the automotive lamp 1 may be a projector-type lamp having a projection lens, for instance.

Claims

An automotive lamp (1) comprising:
a first light source (102) that emits a first laser light (B) having a peak wavelength in a wavelength region of 450 nm to 475 nm (both inclusive);

a second light source (104) that emits a second laser light (G) having a peak wavelength in a wavelength region of 525 nm to 555 nm (both inclusive), wherein an interval between the peak wavelength of the first laser light (B) and the peak wavelength of the second laser light (G) is greater than or equal to 65 nm and less than or equal to 95 nm;

a third light source (106) that emits a third laser light (O) having a peak wavelength in a wavelength region of 605 nm to 620 nm (both inclusive), wherein an interval between the peak wavelength of the second laser light (G) and the peak wavelength of the third laser light (O) is greater than or equal to 60 nm and less than 80 nm, and an interval between the peak wavelength of the first laser light (B) and the peak wavelength of the third laser light (O) is less than 170 nm; and

a light condensing unit (200) that collects the first to third laser lights so as to generate a white laser light (W).
The automotive lamp (1) according to claim 1, wherein the third laser light (O) has a peak wavelength in a wavelength region of 610 nm to 620 nm (both inclusive).
The automotive lamp (1) according to claim 1 or claim 2, wherein the first laser light (B) has a peak wavelength in a wavelength region of 450 nm to 470 nm (both inclusive).
The automotive lamp according to one of claims 1 through 3, wherein the first through third light sources (102, 104, 106) are each constituted by a laser diode and are mounted on a common substrate.
The automotive lamp according to one of claims 1 through 4, wherein
the light condensing unit (200) includes:
a first dichroic mirror (202) that reflects the first laser light (B);

a second dichroic mirror (204) that reflects the second laser light (G); and

a third dichroic mirror (206) that reflects the third laser light (O).
The automotive lamp according to one of claims 1 through 5, further comprising:
a first lens (112) provided on a light path of the first laser light (B) between the first light source (102) and the light condensing unit (200) and is constituted by a collimator lens;

a second lens (114) provided on a light path of the second laser light (G) between the second light source (104) and the light condensing unit (200) and is constituted by a collimator lens; and

a third lens (116) provided on a light path of the third laser light (O) between the third light source (106) and the light condensing unit (200) and is constituted by a collimator lens.
The automotive lamp according to one of claims 1 through 6, further comprising:
a scanning unit (300) that scans the laser lights emitted from the first through third light sources (102, 104, 106) and forms a predetermined light distribution pattern.