Abstract:
A headlight for a motor vehicle includes at least two light sources and a driver, which is arranged to vary the light intensities of the light sources with a phase shift to one another periodically between a minimum and a maximum and in the course of a period to set intermediate values between the maximum and the minimum. In a phase of the period, in which the first light source reaches the maximum of its light intensity, the light intensity of the second light source is situated at an intermediate value and increases.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 102015002341.1, filed Feb. 24, 2015, which is incorporated herein by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present disclosure pertains to a headlight for a motor vehicle, and more particularly a blinker light or a multipurpose headlight, in which the blinker light function is combined with one or more other light functions. 
       BACKGROUND 
       [0003]    In recent years, light-emitting diodes or LEDs are being used increasingly as illuminants in vehicle headlights owing to their high degree of efficiency and their small dimensions. In order to achieve the necessary light intensity for the light functions on vehicles, hitherto, often several LEDs had to be operated together in a headlight. Thereby, the possibility arose to switch the several LEDs with a small time offset in a blinker, in order to thus produce in the observer the illusion of a light source moving or spreading out in the headlight. Such so-called dynamic blinkers are enjoying increasing popularity by the public. 
         [0004]    Further technical developments in the light-emitting diodes have led to the fact that in the meantime a small number of light-emitting diodes or even a single light-emitting diode is sufficient, in order to achieve the necessary light intensity for the lighting function of a vehicle. Frequently, the necessary light intensity can be provided with a small number of modern, high-performance light-emitting diodes even more inexpensively than with numerous low-output ones, in any case a reduction in the number of the required light-emitting diodes leads to a simpler manufacture and accordingly lower manufacturing costs and is therefore attractive for the manufacturers. However, the smaller the number of the LEDs, the more jerky the change appears, when these are switched on and off in succession, and the illusion of a moved light source can be produced all the less convincingly. 
       SUMMARY 
       [0005]    The present disclosure provides a headlight for a motor vehicle, in which the illusion of a moved light source can be also be produced in a convincing manner with a small number of light sources. According to a configuration of the present disclosure a headlight for a motor vehicle includes at least two light sources. A driver is configured to vary the light intensities of the light sources with a phase shift to one another periodically between a minimum and a maximum and in the course of a period to set intermediate values between the maximum and the minimum. In one phase of the period, in which the one light source reaches the maximum of its light intensity, the light intensity of the second light source is at an intermediate value and increases. Even if only two light sources are present, the focus of the shared light distribution of the light sources, as it presents itself to the eye of an observer, can assume numerous intermediate positions and can thus bring about the illusion of a continuous movement. By the light intensity of the second light source still increasing at a moment at which the first light source has reached its maximum light intensity, the impression occurs with the observer of a single moved light source, which moves increasingly in the direction of the second light source. When the second light source is positioned nearer to an edge of the headlight than the first, this assists the impression in the observer of a movement away from the center of the vehicle, in lateral direction, corresponding to the maneuver of the vehicle announced by the blinking. 
         [0006]    In order to ensure a sufficient conspicuousness of the light signal for other road users and a reliable detection as a blinker signal, the driver can be arranged to switch over the light intensity of both light sources simultaneously to the minimum. For the conspicuousness of the light signal, it is also expedient if the switchover to the minimum takes place at the moment at which the light intensity of the second light source has reached its maximum. The light intensity of the first light source, on the other hand, can have already decreased again to an intermediate value at the moment of the switchover. 
         [0007]    In order to be able to implement several light functions in the headlight, it is expedient if at least one of the light sources is able to be switched over between the emission of colored, mostly yellow, light for the blinker function described above, and the emission of white light, in particular for a daytime running lamp or parking light function. Such a light source which is able to be switched over can include an illuminant producing the colored light and an illuminant producing a white light, which are operated for producing white or colored light in alternation, or an illuminant producing colored light and at least one complementary illuminant, which is able to be operated at the same time with the colored illuminant and the light of which is able to be superimposed with the colored light to the white light. The fact that the white and the colored light originates from different illuminants can be concealed from the eyes of the observer by the light source, which is able to be switched over, including a diffuser which is beamed at by the differently colored illuminants, at which diffuser the light of the different illuminants can mix and from where it can reach the eye of the observer. 
         [0008]    The headlight can be a blinker- and position indicator lamp, which can be integrated e.g. into the housing of an exterior mirror. It can, however, also concern a front headlight; then, in addition at least a third light source should also be provided, which emits white light, in order to realize a main beam- and/or dipped beam function in one. When the headlight is a taillight, a third light source can emit red or—as a reversing signal—white light. 
         [0009]    A shield of the headlight, viewed from the direction of a beam emitted by the third light source, can be divided into a main region, from which the beam originates, a first edge region, via which the first light source emits, and a second edge region, via which the second light source emits. In order to produce the illusion of an outwardly directed movement, the first edge region extends here expediently between the main region and the second edge region. 
         [0010]    The diffuser preferably has an elongated shape corresponding to the shape of the edge region receiving it. In order to achieve a uniform distribution of the light intensity over the edge region, the diffuser can include a stem section, on which the illuminants are arranged, and two branches proceeding from the stem section. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements. 
           [0012]      FIG. 1  is a diagrammatic view of a headlight; 
           [0013]      FIG. 2  is a section through the headlight along the section plane II-II in  FIG. 1 ; 
           [0014]      FIG. 3  is a section through the headlight along the section plane III-III in  FIG. 1 ; 
           [0015]      FIG. 4  shows a configuration of the diffuser for a second variant; and 
           [0016]      FIG. 5  is a graph representing the light intensity of different light sources of the headlight in the course of time. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description. 
         [0018]      FIG. 1  shows a headlight  1  for a motor vehicle in a diagrammatic view. The headlight  1  is divided according to its different light functions into regions  35 ,  36 ,  37 ,  38 . When a from headlight is concerned, the region  35 , designated as dipped beam region, can contain a light source  4  and a reflector  7 , which bundles the light of the light source  4  to a dipped light beam. The region  36 , designated as main beam region, contains a light source  5  and a reflector  8 , which bundles the light of the light source  5  to a main light beam. The main light beam and dipped light beam are emitted in only slightly different directions and can both be considered as a principal beam of the headlight  1 , which spreads out opposed to the viewing direction onto the headlight  1  in  FIG. 1 . Accordingly, the two regions  35 ,  36  can be considered together as a main region  34  of the headlight  1 . In the case of a taillight, the region  35  could emit red light, whilst the region  37  functions as a reversing signal and emits white light. 
         [0019]    The region  37 , designated as outer edge region, is hook-shaped with an upper leg running along an upper edge of the headlight, and with a lateral leg, which runs along the upper part of a lateral edge of the headlight adjoining a mudguard of the vehicle. The outer edge region  37  contains two elongated diffusers  13 ,  14 , one of which extends in the upper leg and the other in the lateral leg, and a reflector  30  filling the entire outer edge region  37 . The inner edge region  38  enclosed between the first edge region  37  and the main region  34  is hook-shaped and contains in each of its two legs an elongated diffuser  15  or respectively  16  and a reflector  31  extending behind the diffusers  15 ,  16 . 
         [0020]      FIG. 2  shows a section along the section plane II-II in  FIG. 1 . Ends of the diffusers  13 ,  14  are inserted in recesses of a socket  11 . At the bottom of each recess, three illuminants  25 ,  26 ,  27  are arranged so that they radiate through the diffuser  13  or respectively  14  from its inserted end. The diffusers  13 ,  14  emit the irradiated light continuously over their length. The diffusers  15 ,  16  are inserted in the same manner as the diffusers  13 ,  14  into recesses of the socket  11  equipped with the illuminants  25 ,  26 ,  27 . An electronic driver  41  controls the illuminants  25 ,  26 ,  27  of the light sources  2 ,  3 . 
         [0021]    Alternatively, two identically constructed sockets could also be mounted in the headlight  1 , one of which receives the diffusers  13 ,  14  of the outer edge region  37  and the other of which receives the diffusers  15 ,  16  of the inner edge region  38 . The diffusers  13 ,  14  of the outer edge region  37  form together with the illuminants  25 ,  26 ,  27  radiating through them a light source  2 ; a further light source  3  of the inner edge region  38  includes the diffusers  15 ,  16  and the illuminants  25 ,  26 ,  27  thereof. 
         [0022]    The diffusers  13 ,  14 ,  15 ,  16  shown in  FIG. 1  taper proceeding from the end which is received in the socket  11 , towards the other, free end. As the diffusers  13 ,  14 ,  15 ,  16  emit light along their length, the light flux in the diffusers decreases respectively from the socketed end towards the free end. In the case of a diffuser with a constant cross-section, this would result in a decreasing light density towards the free end. As a result of the tapering, also the light-emitting area of the diffusers becomes narrower towards the free end, the decrease of the light density can be reduced or the light density can even be kept constant. 
         [0023]      FIG. 3  shows a section through the headlight along the section plane III-III in  FIG. 1 . The dipped beam region  35  and the edge regions  37 ,  38  are staggered in longitudinal direction of the vehicle; by the second edge region  38  being set back behind the dipped beam region  36  lying therebeneath, and the first edge region  37  being set back behind the second edge region  38  lying therebeneath, a streamlined, swept shape of the headlight  1  is obtained. In the configuration of  FIG. 3 , the diffusers  13 ,  15  have respectively a round cross-section, and the reflectors  30 ,  31  are arranged spaced apart from the diffusers  13 ,  15 . As reflectors  30 ,  31  directly adjoin one another, the edge regions  37 ,  38 , when the illuminants  25 ,  26 ,  27  are simultaneously in operation in both, form a single cohesive luminous area for the eyes of an observer. 
         [0024]    According to a first variant, the reflectors  30 ,  31  can be replaced by a reflecting layer which is applied directly onto a surface of the diffusers  13 ,  14 ,  15 ,  16  facing the interior of the headlight  1 . So that also in this case a single cohesive luminous area is presented to the eyes of an observer, although the diffusers  13 ,  14  and  15 ,  16  of the two edge regions  37 ,  38  are separated by a gap, a glass body, which fours the outer side of the headlight, can be provided in front of the edge regions  37 ,  38  with suitable refractive elements. 
         [0025]      FIG. 4  shows the two diffusers  13 ,  14  for a second variant in a section along a section plane analogous to  FIG. 2 . The ends of the two diffusers  13 ,  14  facing the illuminants are fused here to one another and are received in a shared recess of the socket  11 . The illuminants  25 ,  26 ,  27  arranged in this recess supply both diffusers  13 ,  14 . In this way, illuminants can be saved compared with the embodiment in  FIG. 2 . The diffusers  15 ,  16  can also be embodied according to this second variant. 
         [0026]    According to a first configuration, at each diffuser  13 ,  14 ,  15 ,  16  the illuminant  25  is a red LED, the illuminant  26  a green LED and the illuminant  27  a blue LED, the light of which mixes in the respective diffuser. The color of the LEDs is selected so that their light superimposes to white light with full light intensity. 
         [0027]    To operate the edge region  38  as a daytime running lamp, the driver  41  switches on the LEDs  25 ,  26 ,  27  at the diffusers  15 ,  16 , so that the light source  3  of the edge region  38  emits white light. The light source  2  remains switched off. In order to produce a parking light with lower light intensity as the daytime running lamp, the driver  41  can jointly dim the LEDs  25 ,  26 ,  27  of the light source  3 . Alternatively, the daytime running lamp can be produced by the driver  41  operating the LEDs  25 ,  26 ,  27  of both light sources  2 ,  3  simultaneously with full light intensity and by operating the LEDs  25 ,  26 ,  27  of only one of the light sources  2 ,  3  for the production of a parking light. 
         [0028]    The operation of the headlight as a blinker is explained with the aid of  FIG. 5 .  FIG. 5  shows the light intensity  1  of the red LEDs  25  of the two light sources  2 ,  3  as a function of time t. At a moment t0 the headlight is in operation as a daytime running lamp, and the LEDs  25 ,  26 ,  27  of both light sources  2 ,  3  run with their full light intensity (100%), according to a curve T in  FIG. 5 , up until at moment t1 the vehicle driver sets the blinker. Thereupon, the LEDs  25 ,  26 ,  27  are firstly all switched off or, as illustrated in  FIG. 5 , their light intensity is shut down to 0 in a short time span up to t2. At the moment t2 the first period of the blinker signal begins, by the light intensity of the red LED  25  of the light source  3  gradually being raised again, as illustrated by a curve Bi with long dashes. In order to obtain yellow light, the green LED  26  is raised again in the same manner, whereas the blue LED  27  remains switched off or, in order to precisely adjust a desired shade of color of the yellow blinker light, is operated with a light intensity which is proportional to the light intensity of the LEDs  25 ,  26  but is substantially less. The driver can regulate the light intensity of the LEDs continuously in accordance with the illustration of  FIG. 5 , or it can increase it in a plurality of discrete steps from 0 to 100%. 
         [0029]    When at the moment t3 the light intensity of the LED  25  of the light source  3  has reached a predetermined threshold value of e.g. 50% of its maximum light intensity, the driver  41  also begins to increase the light intensity again in the LED  25  of the light source  2 , illustrated by a curve Ba in short dashed lines. Up to the moment t4, at which the LED  25  of the light source  3  reaches its maximum light intensity, the light intensities of both light sources  2 ,  3  jointly increase, wherein the impression of the observer of a moving light source in this time is based on the increasing relative portion of the light source  2  in the overall brightness of the blinker—illustrated by a curve Bges. 
         [0030]    Starting from the moment t4, the driver  41  regulates the light intensity of the LEDs of the light source  3  down again, which intensifies the illusion of a movement of the light source. In order to generate a typical, chronologically sharply delimited light impulse for a vehicle blinker, the driver does not return the light intensity of the LEDs  25  continuously back to 0, but rather switches it off abruptly at a moment t5 in both light sources  2 ,  3 . In the case considered here, this moment t5 is also the one at which the LED  25  of the light source  2  reaches its maximum light intensity. 
         [0031]    At the moment t5, as shown, a second period of the blinker signal can begin immediately; however, a waiting time could also be provided, in which the LEDs of both light sources  2 ,  3  remain switched off, before the light intensity of the LED  25  of the light source  3  increases again. 
         [0032]    According to a second configuration, the socket  11  is not equipped with three LEDs in the primary colors, but rather each light source  2 ,  3  has respectively a white LED  27  for daytime running lamp and parking light and a yellow LED  25  for the blinker, and the installation space for the LED  26  shown in  FIG. 2 or 4  is missing or remains free. The sequence shown in  FIG. 5  does not change substantially thereby; the curve T shows the light intensity of the white LED  27 ; this remains switched off, as long as the blinker operation continues. The curve Bi shows the light intensity of the yellow LED  25  of the light source  3 , and the curve Ba shows that of the yellow LED  25  of the light source  2  situated closer to the edge of the headlight  1 . 
         [0033]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.