In-vehicle headlight and light projection method

Reliability of an in-vehicle headlight is improved by changing a light distribution pattern without using any mechanical configuration. The in-vehicle headlight includes a laser light source 1, a spatial light modulator 3, a spatial-light-modulator controller, and a projection lens 5. The laser light source 1 emits a laser light beam 10. The spatial light modulator 3 modulates a phase distribution of the laser light beam 10 emitted by the laser light source 1. The spatial-light-modulator controller is provided in a headlight controller 36, and controls the spatial light modulator 3. The spatial-light-modulator controller controls the spatial light modulator 3 so as to modulate the phase distribution of the laser light beam 10, and changes the light distribution pattern projected from the projection lens 5.

CROSS REFERENCE

This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2017/012661, filed on Mar. 28, 2017, the entire contents is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an in-vehicle headlight and a light projection method, particularly, a technique that mounts a laser light source and a spatial light modulator and is effective in controlling light distribution using holography principle.

BACKGROUND ART

For example, a halogen lamp and an HID (High-Intensity Discharge) lamp, etc. have been widely used as light sources for in-vehicle headlamps. Meanwhile, movement to introduce semiconductor light sources recently increases from advantages of having longer lifetimes and faster lighting/extinction start-up than such light sources.

A laser light beam among the semiconductor light sources has high directivity and can easily form a spot beam with high luminance, so that laser light sources have begun to be used as light sources for the in-vehicle headlamps from the viewpoint of improving visibility. For example, Patent Document 1 discloses “The vehicular lighting fixture100of the present embodiment is applied to a headlamp or a fog lamp of a vehicle such as an automobile or a motorcycle, and includes a light emitting unit10, a laser optical system20, a projection lens30, and the like.”

Additionally, consideration for avoidance of glare's occurrence to other vehicles needs to be made in improving visibility.

As an example, an Adaptive Driving Beam (ADB) is proposed and begin to be put to practical use, the Adaptive Driving Beam adaptively controlling light distribution states for avoiding glare's occurrence to forward vehicles and oncoming vehicles while always brightly illuminating a visual field of a driver based on high-beam irradiation.

Particularly, the in-vehicle headlamps using the laser light sources are increasingly concerned about the glare's occurrence to the oncoming vehicles and the preceding vehicles as illuminance is made high, so that adaptively controlling the light distribution states is important.

For example, Patent Document 2 discloses, as a technique for controlling light distribution patterns of in-vehicle headlamps using laser light sources, “By controlling lighting intensity of light sources and inclinations of mirror members to scan, on a phosphor panel, light emitted from the light sources and reflected onto the mirror members in the form of predetermined scanning patterns, visible light beams distributed in shapes and light intensity corresponding to those scanning patterns are emitted from the phosphor panel and are projected in front of the vehicle by a projection lens. Namely, formed are the light distribution patterns corresponding to the scanning patterns on the phosphor panel. Such formation makes it possible to freely change the light distribution patterns only by varying the lighting intensity of the light sources and the inclinations of the mirror members without needing to provide many light emitting units (light sources) similarly to conventional ones.

RELATED ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The in-vehicle headlights are security parts whose equipment is required by law to ensure safety, and demand high reliability over a long period of time. Patent Document 2 described above uses a mechanical mechanism(s) to cause the inclination of the mirror member to change, thereby changing the light distribution patterns. However, when operations by the mechanical mechanism are repeated for a long period of time, abrasion and/or consumption of mechanical parts may occur to no small degree. Consequently, arises a problem of concern about malfunctions associated with such abrasion occurrence.

In the in-vehicle headlight that requires high reliability, it is desirable that the light distribution patterns can be changed by a solid-state component(s) without providing a movable part(s) using a mechanical mechanism as much as possible.

An object of the present invention is to provide, without using a mechanical configuration(s), a technique capable of improving reliability of an in-vehicle headlight by changing light distribution patterns.

The above and other objects and novel characteristics of the present invention will be apparent from the description of the present specification and the accompanying drawings.

Means for Solving the Problems

The following is a brief description of an outline of the typical invention disclosed in the present application.

Namely, atypical in-vehicle headlight includes a laser light source, a spatial light modulator, a controller, and a projection lens. The laser light source emits a laser light beam(s). The spatial light modulator modulates a phase distribution(s) of the laser light beam emitted by the laser light source. The controller controls the spatial light modulator. The projection lens projects emission light of the spatial light modulator.

Then, the controller controls the spatial light modulator so as to modulate the phase distribution of the laser light beam, and change a light distribution pattern(s) projected from the projection lens.

Further, the in-vehicle headlight is provided between the spatial light modulator and the projection lens, and has a phosphor that radiates fluorescence by the laser beam being irradiated. The projection lens projects a light beam generated by mixing the laser light beam and the fluorescence radiated by the phosphor.

Effects of the Invention

The effects obtained by typical embodiments of the invention disclosed in the present application will be briefly described below.

The reliability of the headlight can be improved.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Components having the same function are denoted by the same reference characters throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Hatching may be used even in a plan view so as to make the drawings easy to see.

First Embodiment

Hereinafter, an embodiment will be described in detail.

FIG. 1is a schematic explanatory diagram showing an example of an optical system in a headlight according to the present first embodiment.FIG. 2is an explanatory diagram showing an example in which a phase is added for each pixel of a spatial light modulator, the headlight ofFIG. 1having the spatial light modulator.FIG. 3is an explanatory diagram showing an example in which an optical phase is modulated by the spatial light modulator ofFIG. 2.

The headlight means an in-vehicle headlight mounted on an automobile or the like and, as shown inFIG. 1, includes a headlight unit35and a headlight controller36. The headlight unit35includes a laser light source1, a lens2, a spatial light modulator3, a phosphor4, and a projection lens5.

The headlight controller36generates various light distribution patterns by controlling an irradiation pattern(s) of the headlight unit35. Incidentally, a configuration of the headlight controller36will be described later with reference toFIG. 7.

InFIG. 1, for example, the laser light source1is a laser light source that emits a blue laser light beam, and a laser light beam(s)10emitted from the laser light source1is incident on the spatial light modulator3via the lens2.

For example, as shown inFIG. 2, the spatial light modulator3is a phase-modulation type spatial light modulator that has a plurality of pixels arranged two-dimensionally and modulates a phase of the incident laser light beam10for each pixel. The phase is added to each pixel. For example, a phase of Δϕi,jis added to a pixel of (i, j) as shown inFIG. 2.

FIG. 3Arepresents a state before adding the phase to each pixel, and if a wavefront of an incidence light beam is flat, a wavefront25of an emission light beam remains flat. Meanwhile, as shown inFIG. 3B, a wavefront25of each laser light beam10can be transformed (converted) into a desired shape by adding a predetermined phase to each pixel.

Since a light beam(s) propagates in a direction perpendicular to a wavefront, control of a wavefront shape makes it possible to control light's propagation characteristics. As a result, an irradiation pattern of a light beam separating a predetermined distance therefrom can be controlled to have a desired shape.

Incidentally, a phase amount to be added to each pixel is adjusted by, for example, control etc. of a voltage to each pixel. Used as the spatial light modulator3is a liquid-crystal type spatial light modulator in which: liquid crystals of several hundred to several thousand per side are arranged as a two-dimensional pixel; a voltage is controlled for each pixel; and a phase is modulated by varying orientations of liquid crystal molecules in accordance with the controlled voltage.

Incidentally, an optical system of the headlight unit35may have a configuration using a reflection type spatial light modulator3.

FIG. 4is an explanatory diagram showing an example of a configuration of a headlight unit using a reflection type spatial light modulator.

In this case, as shown inFIG. 4, used as the reflection type spatial light modulator3is a spatial light modulator, in which fine structures of several hundred to several thousand per side are arranged as a two-dimensional pixel on a silicon substrate and the structure corresponding to each pixel moves perpendicularly to a surface to modulate a phase of a predetermined pixel, similarly to a Planar Light Valve manufactured by Silicon Light Machines. Alternatively, used is a spatial light modulator called LCOS (Liquid Crystal On Silicon) in which liquid crystals are arranged (aligned) on a silicon substrate.

Thus, the spatial light modulator3is a solid-state modulator capable of phase modulation without providing a mechanical mechanism(s). Such a modulator brings no occurrence of abrasion and consumption etc. of the mechanical parts, and makes it possible to reduce occurrence of malfunctions etc. of the headlight in accordance with no abrasion occurrence.

InFIG. 1, the laser light beams10are separated into a diffracted beam6aand a 0th order diffracted beam7aby the phase modulation of the spatial light modulator3. Here, the 0th order diffracted beam means a beam transmitted, as it is, without being subjected to phase modulation in a case of a transmission type spatial light modulator. Additionally, in a case of a reflection type spatial light modulator, the 0th order diffracted beam means a beam reflected, as it is, without being subjected to phase modulation. Incidentally, the laser light beams10incident on the spatial light modulator3are not limited to parallel light beams, and may be convergent light beams or divergent light beams.

Blue laser light beams separated into the diffracted beam6aand the 0th order diffracted beam7aare irradiated to the phosphor4with predetermined irradiation patterns, and a spot(s) subjected to this irradiation is excited. For example, fluorescence having a yellow spectrum occurs from the excited spot.

Part of the diffracted beam6aand part of the 0th order diffracted beam7apass through the phosphor4, and a mixture of those laser beams and the fluorescence occurring from the phosphor4becomes a white light beam. The white light beam is used as a headlight, and is projected in front of the headlight through the projection lens5.

Here, for convenience, a white light beam generated by the diffracted beam6ais abbreviated as a white beam6b, and a white light beam generated by the 0th order diffracted beam7ais abbreviated as a white beam7b.

Since the excited spot on the phosphor4becomes a source for generating white beams, irradiation patterns with which the diffracted beam6aand 0th order diffracted beam7aexciting the phosphor4are irradiated onto the phosphor4can be virtually regarded as light source shapes of the white beams.

InFIG. 1, the phosphor4is disposed at, for example, an approximate back focus position of the projection lens5, so that the irradiation patterns of the diffracted beam6aand 0th order diffracted beam7athat are irradiated onto the phosphor4virtually correspond to a shape of a white light source, and this shape is projected in front of the headlight through the projection lens5.

Namely, changing the irradiation patterns of the diffracted beam6aand 0th order diffracted beam7athat are irradiated onto the phosphor4makes it possible to change the light distribution pattern projected in front of the headlight.

Incidentally, although disposing the phosphor4at the approximate back focus position of the projection lens5is described, a case where the projection lens5is a single lens may cause large field curvature. In order that the irradiation pattern irradiated onto the phosphor4is clearly projected in front of the headlight through the projection lens5, the phosphor4desirably has a curved shape following (depending on) the field curvature, but not a planar shape.

Therefore, for example, adopted may be a configuration in which the phosphor4is made no a planar shape but a curved shape and the diffracted beam6aand the 0th order diffracted beam7aare irradiated onto the phosphor having the curved shape.

Additionally, inFIG. 1, all components in an optical system configuration of the headlight unit35use transmission type optical components. However, the optical system configuration of the headlight unit35is not limited to a transmission type optical system configuration, and may be a reflection type optical system configuration using, for example, a reflection type modulator as the spatial light modulator3. Alternatively, it may be a reflection type optical system configuration by the phosphor4being also combined with a reflector.

<Example of Light Distribution Patterns>

FIGS. 5A and 5Bare explanatory diagrams showing examples of an irradiation pattern and a light distribution pattern on the phosphor that the headlight ofFIG. 1has.

FIG. 5Ashows irradiation patterns of the diffracted beam6aand 0th order diffracted beam7athat are irradiated on the phosphor4, andFIG. 5Bshows light distribution patterns of the white beam6band white beam7bthat are projected in front of the headlight through the projection lens5.

Incidentally, althoughFIG. 5Aindicates that each of the irradiation pattern of the diffracted beam6aand 0th order diffracted beam7ahas an elliptical shape. However, this irradiation pattern is not limited to the elliptical shape, and may have another shape in accordance with that of the light distribution pattern of the headlight. At this time, some optical components for shaping in advance the shapes of the laser light beams10incident on the spatial light modulator3may be separately mounted so that the 0th order diffracted beam7ahas a predetermined shape.

For example, as shown inFIG. 5A, when the diffracted beam6ais irradiated onto the phosphor4and on a lower side in a direction vertical to the 0th order diffracted beam7a, the irradiation pattern on the phosphor4is projected so that its image(s) is inverted to an intersection50between an optical axis of the projection lens5and the 0th diffraction beam7a.

As shown inFIG. 5B, the white beam6bgenerated by the diffracted beam6aleads to being irradiated vertically above, i.e., farther than the white beam7bgenerated by the 0th order diffracted beam7a.

FIGS. 6A and 6Bare explanatory diagrams showing another example ofFIGS. 5A and 5B.FIG. 6Ashows another irradiation pattern example ofFIG. 5A, andFIG. 6Bshows other light distribution pattern examples of the white beam6band white beam7bthat are projected in front of the headlight ofFIG. 5B.

For example, as shown inFIG. 6A, by adjusting the phase modulation by the spatial light modulator3, the irradiation pattern on the phosphor4can be changed to some irradiation patterns obtained by dividing the diffracted beam6a.

When the irradiation pattern on the phosphor4is changed fromFIG. 5Ato, for example,FIG. 6A, a light distribution pattern(s) avoiding occurrence of glare to a preceding vehicle20in front of the headlight can be realized as shown inFIG. 6B.

As described above, the spatial light modulator3has the plurality of pixels arranged two-dimensionally, and can modulate the phase of the incident laser light beam for each pixel. That is, by adding an appropriate phase difference to each pixel, the spatial light modulator3serves as a phase hologram that generates desired 0th order diffracted beam and diffracted beam.

Therefore, use of the holography principle makes it possible to change irradiation amounts and irradiation patterns of the diffracted beam6aand 0th order diffracted beam7athat are irradiated onto the phosphor4.

A phase distribution(s) added to the laser light beams by the spatial light modulator3is previously calculated as a phase distribution(s) to be added by the spatial light modulator3by, for example, an Iterative Fourier Transform Algorithm used in a field of a CGH (Computer-generated Hologram) so that the diffracted beam6aand the 0th order diffracted beam7ahave desired irradiation patterns and irradiation amounts on the phosphor4.

Then, based on the calculated phase distribution, the phases of the laser light beams incident on the spatial light modulator3are modulated for each pixel. At this time, in consideration of an initial phase distribution of the laser light beams incident on the spatial light modulator3, the spatial light modulator3may add, to the laser light beams, a distribution(s) obtained by subtracting the above-mentioned initial phase distribution from the calculated phase distribution.

Timing for changing the irradiation pattern may be changed in cooperation with, for example, a driver's switch operation etc., or may be changed adaptively in accordance with an environment (surrounding situation) photographed by an in-vehicle camera etc. installed in the vehicle.

FIG. 7is an explanatory diagram showing an example of a configuration of a headlight controller that the headlight ofFIG. 1has.

The headlight controller36controls alight distribution(s) of the headlight unit35in cooperation with the above-described in-vehicle camera etc. The headlight controller36includes a photographing unit (camera)60, an image processor61, a recognizer (recognition unit)62, a light distribution pattern calculator63, an addition phase calculator64, a spatial-light-modulator controller65, a laser drive controller66, and a controller67.

The controller67controls respective operations of the photographing unit60, the image processor61, the recognizer62, the light distribution pattern calculator63, the additional phase calculator64, the spatial light modulator controller65, and the laser drive controller.

Based on the control by the controller67, the laser drive controller66drives the laser light source1included in the headlight unit35ofFIG. 1, and controls intensity of the laser light beams emitted from the laser light source1.

Information photographed by the photographing unit60installed in the vehicle, i.e., by an in-vehicle camera is appropriately subjected to an image processing(s) by the image processor61, and is sent to the recognizer62. The recognizer62recognizes, for example, a forward vehicle(s), an oncoming vehicle(s), a pedestrian(s), a road sign(s), and traffic lights, etc.

The light distribution pattern calculator63calculates, for example, a light distribution pattern(s) etc. avoiding occurrence of glare based on those pieces of recognition information. Additionally, the light distribution pattern is not limited to avoiding the glare's occurrence and, for example, a light distribution pattern(s), which is positively irradiated to the pedestrian, road sign, or the like recognized by the recognizer62, may be calculated.

The light distribution pattern calculator63calculates an appropriate light distribution pattern(s) in accordance with the environment. The addition phase calculator64calculates, by using the above-described Iterative Fourier Transform Algorithm or the like, the phase distribution added by the spatial light modulator3based on the information calculated by the light distribution pattern calculator63.

Then, the spatial-light-modulator controller65serving as a controller controls the spatial light modulator3in the headlight unit35ofFIG. 1in accordance with the phase distribution calculated by the additional phase calculator64, and causes the white beam(s) to be irradiated in front of the driver.

Here, the optical system configuration of the headlight unit35is not limited to that shown inFIG. 1, and may be another configuration.

<Another Configuration Example of Headlight>

FIG. 8is an explanatory diagram showing another configuration example of the headlight unit35ofFIG. 1.

A headlight unit35shown inFIG. 8is set so as to have a configuration in which a light source unit15and a projector16are separated through an optical fiber13. The light source unit15includes the laser light source1and lenses11,12, and the projector16includes the lens2, the spatial light modulator3, the phosphor4, and the projection lens5.

The lenses11,12are lenses that condense the laser light beam irradiated from the laser light source1. The laser light beam condensed by the lenses11,12is irradiated to the lens2through the optical fiber13.

Since a configuration subsequent to the lens2is almost the same as that shown inFIG. 1, explanation of such a configuration will be omitted. Incidentally,FIG. 8shows a configuration of having two lenses11,12. However, the number of lenses is not particularly limited, and another configuration example may have one lens or have three lenses or more as long as the lens or lenses condenses the laser light beams.

As shown inFIG. 8, adopting the configuration of separating the light source unit15and the projector16from each other through the optical fiber13makes it possible to increase a degree of freedom of installation of the light source unit15. For example, the light source unit15can be installed not in a position close to an engine room where a temperature condition(s) is severe but in a vehicle which is milder in temperature environment than the engine room. This makes it possible to improve reliability of the headlight.

As described above, realized can be the headlight capable of arbitrarily controlling the light distribution pattern without providing any mechanical mechanisms. Realization of such a headlight makes it possible to improve the reliability of the headlight.

Second Embodiment

<Setting Example of Low Beam Area of 0th Order Diffracted Beam>

Described in a second embodiment will be a technique for setting a 0th order diffracted beam to a low beam area.

FIG. 9is an explanatory diagram showing an example of a light distribution pattern irradiated by a headlight according to a second embodiment.FIG. 10is an explanatory diagram showing another example of the light distribution pattern ofFIG. 9.

The light distribution pattern by the second embodiment has, as shown inFIG. 9, a feature of holding (maintaining) an irradiation area of a white beam7bwithin a region21irradiated by a low-beam headlight (hereinafter, called a “low beam” for convenience), the white beam7bbeing generated by the 0th order diffracted beam7a. Incidentally, a schematic diagram of an optical system of the headlight is almost the same as that shown inFIG. 1, and so its explanation will be omitted.

Namely, the white beam7bgenerated by the 0th order diffracted beam7ais used as the low beam. In order to hold the irradiation area of the white beam7bwithin the region21, for example, such an aperture stop(s) that an incident shape of the laser light beam incident on the spatial light modulator3ofFIG. 1has a desired shape may be disposed in an optical path(s).

A light distribution of the low beam is a light distribution obtained by considering occurrence avoidance of glare to the forward vehicles and oncoming vehicles, so that no problem of the glare arises even if the low beam is always lighted up. Meanwhile, if the light distribution of the white beam7bgenerated by the 0th order diffracted beam exceeds the region21irradiated by the low beam as shown inFIG. 10(a)and can irradiate an inside of a region irradiated by a headlight for travel (hereinafter, called a “high beam” for convenience), the phase modulation by the spatial light modulator3needs to be set so as to make the 0th order diffracted beam as small as possible when necessity of avoiding the glare to the forward or oncoming vehicles occurs. In other words, diffraction efficiency of the laser light beams incident on the spatial light modulator3needs to be almost 100%.

However, a desired phase distribution may not be generally added faithfully to the laser light beams due to an influence of a quantization error(s) etc. associated with a pixel gap(s) and a gradation number(s) of the phase modulation of the spatial light modulator. To be unable to add a desired phase distribution(s) brings deterioration (reduction) in the diffraction efficiency, which may make a value of intensity of the 0th order diffracted beam larger than an assumed value(s).

For this reason, even if the phase modulation is performed by the spatial light modulator3so as to make the 0th order diffracted beam as small as possible, for example, there arises a case of being unable to ignore intensity of an unnecessary 0th order diffracted beam as shown inFIG. 10(b), which causes the white beam7bgenerated by the 0th order diffracted beam to be irradiated to the oncoming vehicle30and the forward vehicle and, consequently, the glare may occur.

Therefore, even if the value of the intensity of the 0th order diffracted beam becomes larger than the assumed value, adopted is such a configuration that the irradiation area in which the white beam7bgenerated by the 0th order diffracted beam7ais irradiated is held within the irradiation region of the low beam so as to be capable of avoiding the problem about the glare.

By adopting such a configuration, a light beam(s) arriving in the high-beam irradiation region leads to being only the white beam6bgenerated by the diffracted beam6a. Therefore, in avoiding the glare to the forward vehicles or oncoming vehicles, the diffraction efficiency may be set to almost zero so that the diffracted beam6ais not generated. This is possible by not performing the phase modulation by the spatial light modulator3.

Adopting such a configuration is effective also from the viewpoint of functional safety in order that the white beam7bgenerated by the 0th order diffracted beam7amay be irradiated in the low-beam irradiation region even if the phase modulation cannot be performed due to a failure(s) of the spatial light modulator3.

Incidentally, inFIGS. 6A and 6B, the irradiation area of the white beam7bis smaller than the irradiation region21of the low beam. However, the present embodiment is not limited to this, and the white beam7bmay be irradiated so as to fill the entire region21therewith.

Further, luminance in the region to which the low beam is irradiated may be given by such a light distribution(s) that the luminance complies with luminance corresponding to each measurement point described in, for example, Section 6.2.4. etc. of the European law (ECE 112).

As described above, the reliability of the headlight can be further improved.

Third Embodiment

<Example of Control of Irradiation Angle>

In this third Embodiment, explained will be a control technique of irradiation angles about a headlight.

FIGS. 11A and 11Bare explanatory diagrams showing examples of an irradiation pattern and a light distribution pattern on a phosphor that a headlight according to a thirty-third embodiment has.

Incidentally, a schematic diagram of the optical system of the headlight is almost the same as that shown inFIG. 1, and a difference therebetween is irradiation patterns of the diffracted beam6aand the 0th order diffracted beam7athat are irradiated to the phosphor4inFIG. 1.

FIG. 11Ashows irradiation patterns of the diffracted beam6aand the 0th order diffracted beam7athat are irradiated onto the phosphor4inFIG. 1, andFIG. 11Bshows light distribution patterns of the white beam6band the white beam7bthat are projected in front of the headlight through the projection lens5inFIG. 1.

In this case, the diffracted beam6ais irradiated, on the phosphor4, sideways in a direction horizontal to the 0th order diffracted beam7a. That is, as shown inFIG. 11A, the diffracted beam6ais irradiated on a right side of the 0th order diffracted beam7a.

As described above, the irradiation pattern on the phosphor4is projected with the image being reversed to the intersection50with the optical axis of the projection lens5. Therefore, as shown inFIG. 11B, the white beam6bgenerated by the diffracted beam6ais shifted, in front of the headlight, horizontally outward farther than the white beam7bgenerated by the 0th order diffracted beam7a, that is, is irradiated so as to extend (expand) a range of irradiation angles.

This makes it possible to bring an increase in light amounts in a wide range in a horizontal direction, and improve horizontal visibility of a driver.

Timing for extending an irradiation-angle range may be cooperated with, for example, a predetermined operation(s) of the driver, or be automatically set in accordance with an in-vehicle camera(s) installed in the vehicle, that is, in accordance with an environment(s) captured by the photographing unit60inFIG. 7.

FIGS. 12A and 12Bare explanatory diagrams showing a concrete example of the light distribution pattern ofFIGS. 1A and 11B.

FIG. 12Ashows an irradiation state before the vehicle reaches a traffic intersection, andFIG. 12Bshows, subsequently toFIG. 12A, a state of extending a horizontal irradiation area when the vehicle reaches the traffic intersection.

InFIG. 12A, the white beam7bgenerated by the 0th order diffracted beam7ais irradiated. Here, when the in-vehicle camera installed in the vehicle recognizes the traffic intersection and the vehicle reaches the traffic intersection, the white beam6bgenerated by the diffracted beam6ais irradiated and the horizontal irradiation area is extended as shown inFIG. 12B.

Such extension makes it possible to improve the visibility when the vehicle travels in the traffic intersection, and to easily recognize a pedestrian(s) etc.

Incidentally, the timing for extending the irradiation area may be extended (increased) in cooperation with a steering angle of a steering wheel when the steering angle of the steering wheel is equal to or larger than a predetermined angle.

FIGS. 13A and 13Bare explanatory diagrams showing another example of the light distribution pattern ofFIGS. 12A and 12B.

FIG. 13Ashows an example of a light distribution pattern in a state where a pedestrian80is present on a side road and the vehicle is traveling in a direction of approaching the pedestrian.FIG. 13Bhas shown an example of the light distribution pattern when the camera recognizes the pedestrian on the side road.

When the vehicle is traveling as shown inFIG. 13Aand the in-vehicle camera installed in the vehicle recognizes the pedestrian80, the white beam6bgenerated by the diffracted beam6ais irradiated and, as shown inFIG. 13B, the horizontal irradiation area is extended. This makes it possible to improve visibility with respect to the pedestrian on the side road.

Incidentally, althoughFIGS. 11A and 11Bshows an example in which the white beam6bgenerated by the diffracted beam6ais irradiated sideways on the road, the irradiation pattern is not limited to this. For example, in order to positively irradiate a pedestrian(s) and a road sign(s), etc., the phase distribution added by the spatial light modulator3can be also changed so that the diffracted beam6ais irradiated to a position on the corresponding phosphor4.

As described above, safety can be enhanced while the reliability of the headlight is improved.

Fourth Embodiment

<Setting of Laser Intensity and Diffraction Efficiency>

A fourth Embodiment changes emission intensity of the laser light beams emitted from the laser light source1in accordance with a light distribution pattern(s) projected from the projection lens5. Incidentally, the headlight is almost the same as that of the first embodiment shown inFIG. 1, and so its explanation will be omitted.

FIGS. 14A-14Dare explanatory diagrams showing examples of an irradiation pattern and a light distribution pattern on a phosphor that a headlight according to the fourth embodiment has.

In this case, for example, as shown inFIG. 14A, irradiated onto the phosphor4are one 0th order diffracted beam7aand five beam spots of a diffracted beam6abelow the 0th order diffracted beam7a. Consequently, as shown inFIG. 14B, white beams6bgenerated by these beam spots and a white beam7bare projected in front of the headlight.

Incidentally, an irradiation pattern(s) irradiated onto the phosphor4is not limited to that ofFIG. 14A, and each shape and the number of beam spots may be changed as the need arises.

Subsequently, for example, it is assumed that an oncoming vehicle30appears from a state shown inFIG. 14Band necessity to avoid glare to the oncoming vehicle30occurs. In this case, the headlight controller36changes the phase modulation by the spatial light modulator3to reduce, for example, one beam spot of the diffracted beam6aon the phosphor4as shown inFIG. 14Cand to irradiate four beam spots of the diffracted beam6a.

At this time, if luminance of lighting areas other than an area extinguished to avoid the glare is changed, the driver feels uncomfortable. Therefore, it is desirable that the luminance of the respective lighting areas is kept substantially the same.

Thus, as shown inFIG. 14D, it is desirable that the respective light amounts of white beam6band white beam7bare set to the same level as that of the light amounts in the respective areas shown inFIG. 14C. That is, inFIG. 14D, the entire amount of light beams projected in front of the headlight leads to being projected as an amount of 90 obtained by summing the numeral values in parentheses.

Therefore, if part of the area is extinguished (lighted off) to avoid the glare, the entire amount of light beams projected in front of the headlight can be reduced from 100 to 90. In other words, reduced can be the emission intensity of the laser light beams emitted from the laser light source1.

The laser drive controller66reduces the emission intensity of the laser light beams emitted from the laser light source1when the light distribution pattern projected in front of the headlight is partially extinguished.

Further, if the diffraction efficiency is focused on, the entire light amount of white beams6bgenerated by the diffracted beam6ain the light distribution pattern shown inFIG. 14Bis projected as an amount of 50 obtained by summing the numeral values in the parentheses.

Meanwhile, the total light amount of light beams projected in front of the headlight is projected as the amount of 100 as described above, so that diffraction efficiency can be estimated to be approximately 50% if vignetting and stray light of a light flux are ignored.

Similarly, when the diffraction efficiency is roughly estimated in the light distribution pattern shown inFIG. 14B, it is estimated as 44% from a relationship of the total light amount90with respect to the entire light amounts40of white beam6bgenerated by the diffracted beam6a.

Namely, partially extinguishing the light distribution pattern projected in front of the headlight makes it possible to reduce the emission intensity of the laser light beam emitted from the laser light source1as described above and to further reduce the diffraction efficiency.

A technique for reducing diffraction efficiency while a diffraction angle is held can be realized by, for example, in a case of a diffraction grating, changing depth of each grating groove, in other words, phase depth while its grating pitch is held.

In consideration of this, for example, in order to realize the irradiation pattern of the diffracted beam6awith the maximum diffraction efficiency, the headlight controller36first calculates a phase distribution(s) required by the spatial light modulator3for the laser light beams through, for example, the Iterative Fourier Transform Algorithm etc.

Then, this calculation can be realized by the spatial light modulator3adding, to the laser light beams, a distribution in which the phase distribution is multiplied by a uniform correction coefficient α to change the phase depth. The correction coefficient α may be set appropriately in accordance with an amount of reduction in diffraction efficiency and, for example, setting the correction coefficient α to a value smaller than 1 makes it possible to reduce the diffraction efficiency.

Incidentally, each numerical value in the parentheses described inFIGS. 14A-14Dare numerical values set for convenience of explanation, and each numerical value is not limited to those numerical values described in Figure.

Also by the above, the present embodiment can enhance safety while improving the reliability of the headlight.

Fifth Embodiment

In a fifth embodiment, a headlight generating an infrared light beam will be described.

A semiconductor light source such as a laser has advantages of having longer lifetime and quicker lighting/extinction start-up than a halogen lamp etc. Meanwhile, the halogen lamp etc. have a feature of almost no spectral component in an infrared light region contained therein.

Infrared light plays an important role as a light source for night vision use applications that enhance night-time visibility. Therefore, the present embodiment mounts the laser light source1for generating a white beam(s) and, for example, needs to separately mount an infrared light source as a separate light source when infrared light is also required for the night vision use applications. An increase in the number of light sources affects increases in size and cost of an apparatus (devise), so that the number of light sources is desirably as small as possible.

Hereinafter, generation of infrared light by the headlight will be described.

FIG. 15is a schematic explanatory diagram of a phosphor that a headlight according to the fifth embodiment has.

Incidentally, a configuration of the headlight is almost the same as that ofFIG. 1in the first embodiment, but a difference between the present embodiment and that ofFIG. 1is a configuration of a phosphor4.

In this case, as shown inFIG. 15, the phosphor4is a phosphor4radiating a yellow spectrum as fluorescence by excitation of the blue laser described above, and is doped with fluorescent materials70each of which radiates fluorescence of infrared light. The phosphor4is a first fluorescent material, and the fluorescent material70is a second fluorescent material.

Incidentally, used as the fluorescent material is a material such as a quantum cutting phosphor which absorbs one high energy photon and emits two lower energy photons, so that use of such a material makes it possible to generate a fluorescent71in a range of a band of near infrared light from a wavelength band of a blue laser.

Adopting such a configuration as the phosphor4makes it possible to generate the fluorescence of yellow light and near infrared light while a single excitation light source and the phosphor4are used.

As described above, the present embodiment can generate the white beams and the near infrared light that are usable as an in-vehicle headlight with a simple configuration.

Additionally, when a divergence angle of fluorescence having a yellow spectrum generated from the phosphor4is different from a divergence angle of a blue laser that has passed through the phosphor4, a region that is not partially mixed therewith and is made no white beam may occur. Therefore, for example, adopted may be such a configuration as to arrange an optical component(s) having wavelength selectivity immediately after the phosphor4, widen the divergence angle of the blue laser, and approach the divergence angle of the fluorescence.

As described above, the present embodiment can enhance nighttime safety while improving the reliability of the headlight.

In the foregoing, the invention made by the inventor of the present invention has been concretely described based on the embodiments. However, needless to say, the present invention is not limited to the foregoing embodiments, and various modifications and alterations can be made within a range not departing from the gist of the present invention.

Note that the present invention is not limited to the embodiments described above and includes various modification examples. For examples, the embodiments above have been described in detail so as to make the present invention easily understood, and the present invention is not always limited to the embodiment having all of the described constituent elements.

Also, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment, and the configuration of one embodiment may be added to the configuration of another embodiment. Furthermore, another configuration may be added to a part of the configuration of each embodiment, and a part of the configuration of each embodiment may be eliminated or replaced with another configuration.

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