Patent Publication Number: US-11035543-B2

Title: Lamp unit

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2018-046662, filed on Mar. 14, 2018 and International Patent Application No. PCT/JP2019/009780, filed on Mar. 11, 2019, the entire content of each of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lamp unit. 
     2. Description of the Related Art 
     Vehicle lamp units adapted to irradiate a scenery in front of a vehicle with a predetermined light distribution pattern by selectively reflecting light output from a light source, using a reflecting device provided on its surface with a plurality of reflective elements arranged in a matrix to (patent document 1). A large number of reflective elements are arranged in a tiltable manner in the reflective device. It is possible to switch the position of the large number of reflective elements between the first position and the second position. The reflecting device is configured to form a light distribution pattern for illuminating the road surface, etc. by appropriately changing the position of each reflective element to the first position at which the direction of reflection of the light from the light source contributes to the formation of a light distribution pattern or to the second position at which the direction of reflection does not contribute to the formation of a light distribution pattern. 
     [Patent Literature] JP2016-110760 
     The aforementioned lamp unit is configured to form a desired light distribution pattern in a space in front of the vehicle by selectively reflecting light output from a single light source. Therefore, the elements of the lamp unit are arranged to adapt to a single light source. Accordingly, the elements of the lamp unit are not optimally arranged in the case a plurality of light sources are employed. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above-described issue, and an illustrative purpose thereof is to provide a novel lamp unit capable of using light output from a plurality of irradiating optical systems efficiently. 
     A lamp unit according to an embodiment of the present invention includes: a projective optical system; a light deflector that is provided behind the projective optical system and selectively reflects incident light toward the projective optical system; a first irradiating optical system that irradiates a reflecting part of the light deflector with first light; and a second irradiating optical system that irradiates the reflecting part of the light deflector with second light. The first irradiating optical system and the second irradiating optical system are arranged such that a direction of irradiation by the first light and a direction of irradiation by the second light are not parallel when a front of the reflecting part is viewed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described, by way of example only, with reference to the accompanying drawings that are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several figures, in which: 
         FIG. 1  is a side view schematically showing a general configuration of the lamp unit according to the embodiment; 
         FIG. 2  is a top view schematically showing a general configuration of the lamp unit according to the embodiment; 
         FIG. 3  is a front view schematically showing a general configuration of the lamp unit according to the embodiment; 
         FIG. 4  is a perspective view schematically showing a general configuration of the lamp unit according to the embodiment; 
         FIG. 5A  is a front view showing a schematic configuration of the light deflector according to the embodiment, and  FIG. 5B  is an A-A cross-sectional view of the light deflector shown in  FIG. 5A ; 
         FIG. 6A  is a schematic diagram showing how the mirror element reflects the light output from the light source of the first irradiating optical system at the reflecting position P 1 ,  FIG. 6B  is a schematic diagram showing how the mirror element reflects the light output from the light source of the first irradiating optical system at the reflecting position P 2 , and  FIG. 6C  is a schematic diagram showing how the light output from the light source of the first irradiating optical system is spread when reflected by the mirror element at the first reflecting position P 1  and the second reflecting position P 2 ; 
         FIG. 7A  is a schematic diagram showing how the mirror element reflects the light output from the light source of the second irradiating optical system at the reflecting position P 2 ,  FIG. 7B  is a schematic diagram showing how the mirror element reflects the light output from the light source of the second irradiating optical system at the reflecting position P 1 , and  FIG. 7C  is a schematic diagram showing how the light output from the light source of the second irradiating optical system is spread when reflected by the mirror element at the first reflecting position P 1  and the second reflecting position P 2 ; 
         FIG. 8  is a schematic diagram showing the pivot shaft of the mirror element according to the embodiment; 
         FIG. 9A  is a front view schematically showing a relationship between the incident light Lin from the first irradiating optical system, the reflected light R 1 , and the reflected light R 2 ,  FIG. 9B  is a front view schematically showing a relationship between the incident light Lin′ from the second irradiating optical system, the reflected light R 1 ′, and the reflected light R 2 ′, and  FIG. 9C  is a front view schematically showing how the states of  FIG. 9A  and  FIG. 9B  are superimposed; and 
         FIG. 10A  is a front view schematically showing a relationship according to the embodiment between the incident light Lin from the first irradiating optical system, the reflected light R 1 , and the reflected light R 2 ,  FIG. 10B  is a front view schematically showing a relationship according to the embodiment between the incident light Lin′ from the second irradiating optical system, the reflected light R 1 ′, and the reflected light R 2 ′, and  FIG. 10C  is a front view schematically showing how the states of  FIG. 10A  and  FIG. 10B  are superimposed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the invention will be described based on preferred embodiments with reference to the accompanying drawings. Identical or like constituting elements, members, processes shown in the drawings are represented by identical symbols and a duplicate description will be omitted. The embodiments do not intend to limit the scope of the invention but exemplify the invention. Not all of the features and the combinations thereof described in the embodiments are necessarily essential to the invention. 
     A lamp unit according to an embodiment of the present invention includes: a projective optical system; a light deflector that is provided behind the projective optical system and selectively reflects incident light toward the projective optical system; a first irradiating optical system that irradiates a reflecting part of the light deflector with first light; and a second irradiating optical system that irradiates the reflecting part of the light deflector with second light. The first irradiating optical system and the second irradiating optical system are arranged such that a direction of irradiation by the first light and a direction of irradiation by the second light are not parallel when a front of the reflecting part is viewed. 
     This inhibits the first light that is not reflected toward the projective optical system when the first light radiated by the first irradiating optical system is reflected by the light deflector from interfering with the second irradiating optical system. Similarly, the second light that is not reflected toward the projective optical system when the second light radiated by the second irradiating optical system is reflected by the light deflector is inhibited from interfering with the first irradiating optical system. This increases the flexibility of arrangement and configuration of the irradiating optical systems and makes it possible to use more of the light radiated by the respective irradiating optical systems in the projective optical system. 
     The light deflector may be configured such that at least a partial region of the reflecting part is adapted to be switched, around a pivot shaft, between i) a first reflecting position that reflects light radiated by the first irradiating optical system or the second irradiating optical system toward the projective optical system such that reflected light is effectively used as part of a light distribution pattern and ii) a second reflecting position that reflects light radiated by the first irradiating optical system or the second irradiating optical system such that reflected light is not effectively used, the first irradiating optical system may be provided on one side of the pivot shaft when a front of the reflecting part is viewed, and the second irradiating optical system may be provided on the other side of the pivot shaft when the front of the reflecting part is viewed. Since the first irradiating optical system and the second irradiating optical system can be provided on both sides of the light deflector, the incidence direction of the light traveling toward the reflecting part of the light deflector can be properly set without considering the interference between the irradiating optical systems. 
     The first irradiating optical system may be arranged to irradiate the reflecting part diagonally with the first light when the front of the reflecting part is viewed, and the second irradiating optical system may be arranged to irradiate the reflecting part diagonally with the second light when the front of the reflecting part is viewed. This can reduce the width of the lamp unit. 
     The light deflector may include a micromirror array. This allows light distribution patterns of various shapes to be formed promptly and accurately. 
     The projective optical system may include a projection lens. The light deflector may be configured such that the first light and the second light reflected at the second reflecting position are not incident on the projection lens. This inhibits occurrence of stray light. 
     Optional combinations of the aforementioned constituting elements, and implementations of the invention in the form of methods, apparatuses, and systems may also be practiced as additional modes of the present invention. 
     [Lamp Unit] 
       FIG. 1  is a side view schematically showing a general configuration of the lamp unit according to the embodiment.  FIG. 2  is a top view schematically showing a general configuration of the lamp unit according to the embodiment.  FIG. 3  is a front view schematically showing a general configuration of the lamp unit according to the embodiment.  FIG. 4  is a perspective view schematically showing a general configuration of the lamp unit according to the embodiment. 
     The lamp unit  10  according to the embodiment includes a projective optical system  12 , a light deflector  100  provided behind the projective optical system  12  and on a light axis Ax and selectively reflecting incident light to the projective optical system  12 , and a first irradiating optical system  16  and a second irradiating optical system  17  for irradiating a reflecting part  100   a  of the light deflector  100  with the light. The projective optical system  12  includes a first projection lens  18   a  and a second projection lens  18   b . The irradiating optical system  16  includes a light source  20  and a reflector  22 . The irradiating optical system  17  includes a light source  24  and a reflector  26 . 
     The lamp unit  10  according to the embodiment is main used as a vehicle lamp (e.g., vehicle head lamp). The application is not limited to this, and the embodiment is also applicable to lamps in illuminating devices and mobile objects (airplanes, rail cars). 
     A semiconductor light emitting device such as a light emitting diode (LED), a laser diode (LD), and an electroluminescence (EL) device, etc., an electric bulb, an incandescent lamp (halogen lamp), a discharge lamp, or the like may be used as the light source  20  and the light source  24 . A light condensing member may be provided between the light source and the reflector. The light condensing member is configured to guide much of the light output from the light source to the reflecting surface of the reflector. For example, a convex lens, a solid shell-shaped light guide, a reflecting mirror having a reflecting inner surface, etc. is used. More specifically, the light condensing member may be a compound parabolic concentrator. In the case most of the light output from the light source can be guided to the reflecting surface of the reflector, the light condensing member need not be used. For example, the light source is mounted at a predetermined position of a heat sink made of a metal, a ceramic, etc. 
     The light deflector  100  is provided on the light axis X of the projective optical system  12  and is configured to selectively reflect the light output from the light source  20  and the light source  24  to the projective optical system  12 . For example, the light deflector  100  is an arrangement of a plurality of micromirrors in an array (matrix) such as a micro electro-mechanical system (MEMS) and a digital mirror device (DMD). By controlling the angle of the reflecting surface of each of the plurality of these micromirrors, the direction of reflection of the light output from the light source  20  and the light source  24  can be selectively changed. In other words, the light deflector  100  can reflect a portion of the light output from the light source  20  and the light source  24  toward the projective optical system  12  and reflect the other portion of the light in a direction in which the light is not effectively used. The direction in which the light is not effectively used can be understood as a direction in which the impact of reflected light is small (e.g., the direction in which the reflected light contributes little to the formation of a desired light distribution pattern) or the direction in which the reflected light travels toward a light absorbing member (light shielding member). 
     The micromirror array of the light deflector  100  described later is arranged in the neighborhood of the composite focal point of the first projection lens  18   a  and the second projection lens  18   b  of the projective optical system  12  according to the embodiment. The projective optical system  12  may include one optical member such as a lens or three or more optical members. The optical member included in the projective optical system is not limited to a lens and may be a reflecting member. 
     The first irradiating optical system  16  according to the embodiment includes a reflector  22  that reflects the light output from the light source  20  toward the light deflector  100 . The reflector  22  is configured to focus the reflected light on the reflecting part  100   a  of the light deflector  100 . This allows the light output from the light source  20  to travel toward the reflecting part  100   a  of the light deflector  100  efficiently. 
     Similarly, the second irradiating optical system  17  according to the embodiment includes a reflector  26  that reflects the light output from the light source  24  toward the light deflector  100 . The reflector  26  is configured to focus the reflected light toward the reflecting part  100   a  of the light deflector  100 . This allows the light output from the light source  24  to travel toward the reflecting part  100   a  of the light deflector  100  efficiently. 
     A reflecting surface  22   a  of the reflector  22  and a reflecting surface  26   a  of the reflector  26  have a larger area than the reflecting part  100   a  of the light deflector  100 . This can reduce the size of the light deflector  100 . The lamp unit  10  configured as described above can be used in a variable light distribution headlamp that can be turned on or off in part. 
     [Light Deflector] 
       FIG. 5A  is a front view showing a schematic configuration of the light deflector according to the embodiment, and  FIG. 5B  is an A-A cross-sectional view of the light deflector shown in  FIG. 5A . 
     As shown in  FIG. 5A , the light deflector  100  according to the embodiment includes a micromirror array  104  in which a plurality of fine mirror elements  102  are arranged in a matrix, and a transparent cover member  106  provided in front of reflecting surfaces  102   a  of the mirror elements  102  (to the right of the light deflector  100  shown in  FIG. 5B ). For example, the cover member is made of glass, plastic, etc. 
     Each mirror element  102  of the micromirror array  104  can be switched between a reflecting position P 1  (the position indicated by the solid line shown in  FIG. 5B ) at which the mirror element  102  reflects the light output from the light source  20  of the first irradiating optical system  16  toward the projective optical system such that the reflected light is effectively used as part of a desired light distribution pattern and a reflecting position P 2  (the position indicated by the broken line shown in  FIG. 5B ) at which the mirror element  102  reflects the light output from the light source such that the reflected light is not effectively used. 
       FIG. 6A  is a schematic diagram showing how the mirror element  102  reflects the light output from the light source  20  of the first irradiating optical system  16  at the reflecting position P 1 ,  FIG. 6B  is a schematic diagram showing how the mirror element  102  reflects the light output from the light source  20  of the first irradiating optical system  16  at the reflecting position P 2 , and  FIG. 6C  is a schematic diagram showing how the light output from the light source  20  of the first irradiating optical system  16  is spread when reflected by the mirror element at the first reflecting position P 1  and the second reflecting position P 2 . For brevity of the description,  FIGS. 6A-6C  illustrate the micromirror array as being replaced by one mirror element. 
     As shown in  FIG. 6C , the incident light Lin is not a completely parallel light because the light output from the light source  20  is condensed and reflected by the reflector  22 . In other words, the incident light Lin incident on the reflecting surface  102   a  of the mirror element  102  has a certain angular spread. The mirror element  102  is arranged such that the reflected light R 1  produced by the reflection of the incident light Lin at the reflecting position P 1  mainly travels toward the projection lens  18   a  ( 18   b ). Further, as shown in  FIG. 6C , the mirror element  102  is arranged such that the reflected light R 2  produced by the reflection of the incident light Lin at the reflecting position P 2  does not travel toward the projection lens  18   a.    
     A desired projected image, a desired reflected image, and the first light distribution pattern can be obtained by controlling the reflecting position of each mirror element  102  to selectively change the direction of reflection of the light output from the light source  20 . 
     The lamp unit  10  according to the embodiment is provided with the second irradiating optical system  17  in addition to the first irradiating optical system  16 . 
       FIG. 7A  is a schematic diagram showing how the mirror element  102  reflects the light output from the light source  24  of the second irradiating optical system  17  at the reflecting position P 2 ,  FIG. 7B  is a schematic diagram showing how the mirror element  102  reflects the light output from the light source  24  of the second irradiating optical system  17  at the reflecting position P 1 , and  FIG. 7C  is a schematic diagram showing how the light output from the light source  24  of the second irradiating optical system  17  is spread when reflected by the mirror element at the first reflecting position P 1  and the second reflecting position P 2 . 
     As shown in  FIG. 7C , the incident light Lin′ is not a completely parallel light because the light output from the light source  24  is condensed and reflected by the reflector  26 . In other words, the incident light Lin′ incident on the reflecting surface  102   a  of the mirror element  102  has a certain angular spread. The mirror element  102  is arranged such that the reflected light R 1 ′ resulting from the reflection of the incident light Lin′ at the reflecting position P 2  mainly travels toward the projection lens  18   a  ( 18   b ). Further, as shown in  FIG. 7C , the mirror element  102  is arranged such that the reflected light R 2 ′ resulting from the reflection of the incident light Lin′ at the reflecting position P 1  does not travel toward the projection lens  18   a.    
     A desired projected image, a desired reflected image, and the second light distribution pattern can be obtained by controlling the reflecting position of each mirror element  102  to selectively change the direction of reflection of the light output from the light source  24 . 
     Thus, the light deflector  100  according to the embodiment is configured such that at least some of the mirror elements  102  of the reflecting part  100   a  can be switched, around a pivot shaft  102   b , between i) the reflecting position P 1  or the reflecting position P 2  that are the first reflecting position that reflects the light radiated by the irradiating optical system  16  or the irradiating optical system  17  toward the projective optical system  12  such that the reflected light is effectively used as part of a desired light distribution pattern and ii) the reflecting position P 2  or the reflecting position P 1  that are the second reflecting position that reflects the light radiated by the irradiating optical system  16  or the irradiating optical system  17  such that the reflected light is not effectively used. 
       FIG. 8  is a schematic diagram showing the pivot shaft of the mirror element  102  according to the embodiment. The mirror element  102  has the quadrangular (e.g., square, rhombic, rectangular, parallelogram) reflecting surface  102   a . Each mirror element  102  is configured such that it can be switched between the reflecting position P 1  and the reflecting position P 2  around the pivot shaft  102   b  aligned with the diagonal line of the quadrangular reflecting surface  102   a . This allows light distribution patterns of various shapes to be formed promptly and accurately. The pivot shaft  102   b  of the mirror element  102  according to the embodiment extends in the vertical direction. Further, the mirror element  102  according to the embodiment is configured to be displaced about ±10-±20° between the reflecting position P 1  and the reflecting position P 2  around the pivot shaft  102   b.    
     By using the light deflector  100  in which the mirror elements  102  as described above are arranged in a matrix, a plurality of functions characterized by different light distribution patterns can be realized in the single lamp unit  10 . For example, as shown in  FIG. 6C , a desired light distribution characteristic can be realized by causing each mirror element  102  of the light deflector  100  to reflect the incident light Lin output from the first irradiating optical system  16  toward the projective optical system  12 . Meanwhile, as shown in  FIG. 7C , a desired light distribution characteristic can be realized by causing each mirror element  102  of the light deflector  100  to reflect the incident light Lin′ output from the second irradiating optical system  17  toward the projective optical system  12 . 
     In the case of a lamp unit in which the direction of reflection and the direction of transmittance of a plurality of irradiating optical systems are controlled by a single light deflector, on the other hand, stray light may be produced if another irradiating optical system is located in a region traveled by the reflected light R 2  or the reflected light R 2 ′ of the respective irradiating optical systems. It is therefore desired to arrange each irradiating optical system in a region that does not overlap (interfere with) a region traveled by the reflected light R 2  or the reflected light R 2 ′ as much as possible. 
     By arranging the first irradiating optical system  16  and the second irradiating optical system  17  such that the direction of irradiation by the first light radiated by the first irradiating optical system  16  is opposite (parallel) to the direction of irradiation by the second light radiated by the second irradiating optical system  17  when the front of the reflecting part  100   a  is viewed, however, the second irradiating optical system  17  will be located in the region of the reflected light R 2  and the first irradiating optical system  16  will be located in the region of the reflected light R 2 ′, as shown in  FIG. 6C  and  FIG. 7C . 
     It is therefore necessary to adjust the direction or spread of the light radiated by the first irradiating optical system  16  and the second irradiating optical system  17  to prevent such a situation. More specifically, it is necessary to reduce the angular spread of the incident light Lin and the incident light Lin′ to a certain degree or shift the regions in which the reflected light R 1  and the reflected light R 1 ′ are incident on the first projection lens  18   a.    
       FIG. 9A  is a front view schematically showing a relationship between the incident light Lin from the first irradiating optical system  16 , the reflected light R 1 , and the reflected light R 2 ,  FIG. 9B  is a front view schematically showing a relationship between the incident light Lin′ from the second irradiating optical system  17 , the reflected light R 1 ′, and the reflected light R 2 ′, and  FIG. 9C  is a front view schematically showing how the states of  FIG. 9A  and  FIG. 9B  are superimposed. 
     As shown in  FIG. 9A , the reflected light R 1  from the first irradiating optical system  16  is incident on the right side of the effective region R 3  of the projective optical system  12 . The effective region R 3  is a region in which the light contributing to the light distribution formed in front of the lamp unit  10  is transmitted. Further, as shown in  FIG. 9B , the reflected light R 1 ′ from the second irradiating optical system  17  is incident on the left side of the effective region R 3  of the projective optical system  12 . Therefore, the effective region R 4  of the output light that results when both the first irradiating optical system  16  and the second irradiating optical system  17  are taken into consideration is limited to the central portion of the effective region R 3  of the projective optical system  12  as shown in  FIG. 9C . Further improvements are necessary from the perspective of using the light output from the light source efficiently. 
     In this background, we have arranged the first irradiating optical system  16  and the second irradiating optical system  17  such that the direction of irradiation by the incident light Lin and the direction of irradiation by the incident light Lin′ are not parallel when the front of the reflecting part  100   a  is viewed. 
       FIG. 10A  is a front view schematically showing a relationship according to the embodiment between the incident light Lin from the first irradiating optical system  16 , the reflected light R 1 , and the reflected light R 2 ,  FIG. 10B  is a front view schematically showing a relationship according to the embodiment between the incident light Lin′ from the second irradiating optical system  17 , the reflected light R 1 ′, and the reflected light R 2 ′, and  FIG. 10C  is a front view schematically showing how the states of  FIG. 10A  and  FIG. 10B  are superimposed. 
     As shown in  FIGS. 1 through 4 , the first irradiating optical system  16  according to the embodiment is provided on one side of the pivot shaft  102   b  (the leftward region in  FIG. 3 ) when the front of the reflecting part  100   a  is viewed and is arranged to irradiate the reflecting part  100   a  with the incident light Lin from diagonally below when the front of the reflecting part  100   a  is viewed. The second irradiating optical system  17  is provided on the other side of the pivot shaft  102   b  when the front of the reflecting part  100   a  is viewed and is arranged to irradiate the reflecting part  100   a  with the incident light Lin′ from diagonally below when the front of the reflecting part  100   a  is viewed. 
     As shown in  FIG. 10A , the reflected light R 1  from the first irradiating optical system  16  is incident on the center of the effective region R 3  of the projective optical system  12 . Further, as shown in  FIG. 10B , the reflected light R 1 ′ from the second irradiating optical system  17  is incident on the center of the effective region R 3  of the projective optical system  12 . Therefore, the effective region R 4  of the output light that results when both the first irradiating optical system  16  and the second irradiating optical system  17  are taken into consideration represents most of the effective region R 3  of the projective optical system  12 , which shows that the light output from the light source is efficiently used. 
     In the lamp unit  10  according to the embodiment, the angle of incidence of the center of the incident light Lin and the incident light Lin′ on the reflecting part  100   a  (front view) is in the range of 30-40° below (or above) the horizontal plane. Further, the angle of incidence of the center of the incident light Lin and the incident light Lin′ on the reflecting part  100   a  (top view) is in the range of 30-40° with respect to the plane that includes the surface of the reflecting part  100   a . This can reduce the width of the lamp unit  10 . 
     As described above, the first irradiating optical system  16  and the second irradiating optical system  17  of the lamp unit  10  according to the embodiment can be provided separately on both sides of the light deflector  100 . Accordingly, the incidence direction of the light traveling toward the reflecting part  100   a  of the light deflector  100  can be properly set without considering the interference between the irradiating optical systems. 
     This inhibits the reflected light R 2  that is not reflected toward the projective optical system  12  when the incident light Lin radiated by the first irradiating optical system  16  is reflected by the light deflector  100  from interfering with the second irradiating optical system  17 . Similarly, the reflected light R 2 ′ that is not reflected toward the projective optical system  12  when the incident light Lin′ radiated by the second irradiating optical system  17  is reflected by the light deflector  100  is inhibited from interfering with the first irradiating optical system  16 . This increases the flexibility of arrangement and configuration of the irradiating optical systems and makes it possible to use more of the light radiated by the respective irradiating optical systems in the projective optical system. 
     Further, the light deflector  100  is configured such that the reflected light R 2  produced by the reflection of the incident light Lin at the reflecting position P 2  and the reflected light R 2 ′ produced by the reflection of the incident light Lin′ at the reflecting position P 1  are not incident on the projection lens  18   a . This inhibits occurrence of stray light. 
     A description is given above of a case in which two irradiating optical systems (light sources) are provided. Alternatively, three or more irradiating optical systems may be provided. 
     The embodiments of the present invention are not limited to those described above and appropriate combinations or replacements of the features of the embodiments are also encompassed by the present invention. The embodiments may be modified by way of combinations, rearranging of the processing sequence, design changes, etc., based on the knowledge of a skilled person, and such modifications are also within the scope of the present invention.