Patent Publication Number: US-2021178898-A1

Title: Display device, in particular for a vehicle

Description:
The invention relates to display device which is in particular employed in a vehicle. 
     Displays or similar display devices offering the additional functionality of inputting an operating command are becoming more and more popular for use in the interior of vehicles. To an increasing extent, such display/operating systems are additionally provided with the functionality of recognizing an approaching object in order to activate the display device for inputting an operating command or changing various operating interfaces depending on an approaching object, for example the hand or a finger of a person. For this purpose, such a proximity sensor system operates with optical radiation in the invisible wavelength range and in particular with IR light. The display device itself is provided with a backlighting unit for backlighting the display with visible light. 
     For reducing the overall depth of such display devices it is known to feed the backlight into a light guide plate from the side, said light guide plate being located behind the display. The transmitter and receiver elements for the optical proximity sensor system are in most cases located in an edge area next to the display or the so-called active area of the display. However, this area is not always available so that the freedom of design when devising a display device is limited. 
     In prior art, electric display devices which are equipped with a display with LED backlight and a proximity sensor system are known from US-A-2018/0069609, for example. US-A-2015/0084928 describes a backlighting unit based on the edge light concept. US-A-2015/0084928 illustrates an electric display device equipped with a display and a proximity sensor system. 
     It is an object of the invention to provide a display device, in particular for a vehicle, which is provided with a proximity sensor system that is arranged in a place-saving manner. 
     For achieving this object, a first embodiment of the invention suggests a display device, in particular for a vehicle, comprising
         a display,   a backlighting unit for backlighting the display,   wherein the backlighting unit comprises a plurality of light sources for backlight and a light guide plate having a light emission side facing the display, an opposite rear side and a circumferential side edge surface arranged between the light emission side and the rear side,   wherein the light sources are arranged next to the light guide plate in a laterally offset manner for feeding light through at least a partial area of the side edge surface of the light guide plate into the latter, and backlight fed into the light guide plate from the side is emitted from the light emission side of the light guide plate, and   a proximity sensor system for sensing an object, such as a hand of a person, for example, located in the area in front of the display,   wherein the proximity sensor system comprises at least one proximity sensor system transmitter element for transmitting invisible sensor radiation, in particular IR sensor radiation, and at least one proximity sensor system receiver element for receiving sensor radiation reflected from an object in the area in front of the display,   wherein the at least one proximity sensor system transmitter element is arranged laterally offset from an area of the side edge surface of the light guide plate and the sensor radiation in this area is fed into the side edge surface of the light guide plate and is emitted from the light emission side of the light guide plate, and   wherein the at least one proximity sensor system receiver element is arranged inside the display and/or between the display and the light guide plate and/or behind the light guide plate.       

     The display device according to the invention is provided with a display and a backlighting unit, arranged behind the display, for backlighting the display. This backlighting unit operates according to the so-called edge light concept where backlight is fed into a light guide plate from the side. The light guide plate is located behind the display and comprises a light emission side, a rear side opposite the light emission side and a circumferential side edge surface. The light sources of the backlighting unit are arranged opposite the side edge surface such that its backlight is fed into the light guide plate via the side edge surface where corresponding measures cause the backlight to be internally reflected to the light emission side and thus to be emitted from the light emission side and then through the display. 
     According to the invention, in the first variant, the sensor radiation of the at least one proximity sensor system transmitter element is also fed into a partial area of the side edge surface of the light guide plate. In the light guide plate, this sensor radiation, like the backlight, is deflected towards the light emission side and then penetrates the display and thus travels into the space or the area upstream of the display for being received by one or a plurality of proximity sensor system receiver elements after having been reflected from an object (hand, finger) located in this area. The received signals are processed in an evaluation unit which generally also controls the proximity sensor system transmitter elements and the at least one proximity sensor system transmitter element, respectively. For example, in the case of a plurality of proximity sensor system transmitter elements, they can be sequentially or cyclically controlled such that receive signals can be received by the proximity sensor system receiver elements distributedly arranged across the display for detecting in which area in front of the display an object is located. Thus, the object recognition can be realized at a specific resolution determined by the density of transmitter and receiver elements of the proximity sensor system. 
     Generally, it is advantageous when a reflector reflecting the backlight and the sensor radiation is arranged on the rear side of the light guide plate, or when the rear side of the light guide plate comprises a reflective coating reflecting the back light or the sensor radiation. 
     Typically, a particularly intensive illumination of the display with backlight is desired. This means that along the side edge surface of the light guide plate backlight sources are already tightly packed. If, therefore, there is no space left for the proximity sensor system transmitter elements between these backlight sources, it is appropriate to arrange these proximity sensor system transmitter elements above or below the backlight sources. This means that the light guide plate must be of a thicker configuration such that two rows of radiation sources, namely the backlight sources on the one hand and the proximity sensor system transmitter elements on the other hand can be arranged one above the other. However, the manufacture of the light guide plate by injection molding could be problematic due to the required larger thickness of the light guide plate as compared to the first approach of the first variant of the concept according to the invention presented above. 
     Thus, it is advantageous when the light guide plate comprises an upper light guide material layer having a circumferential upper side edge surface and a lower light guide material layer having a circumferential lower side edge surface, wherein the light sources feed backlight into at least a partial area of the upper side edge surface and the at least one proximity sensor system transmitter element feeds sensor radiation into at least a partial area of the lower side edge surface. In this approach, the light guide plate thus comprises two light guide material layers which are integrally formed with each other or separate from each other. In other words, two light guide plate elements are employed. Each light guide plate element serves for deflecting a different radiation. Thus, the upper light guide plate element deflects the backlight for causing it to be emitted from the light emission side of the light guide plate facing the display. The lower light guide plate element receives the sensor radiation and deflects it towards the display. Thus, the sensor radiation also passes through the upper light guide material layer and is emitted therefrom. The advantage of using two light guide plate elements is that each light guide material layer for the radiation fed into the light guide material layer and deflected there can be optimized with regard to both the material as well as the radiation and the internal configuration required for the homogeneous lateral radiation emission. 
     The concept described above can also be inversely employed such that the light sources feed backlight into at least a partial area of the lower side edge surface and the at least one proximity sensor system transmitter element feeds sensor radiation into at least a partial area of the upper side edge surface. 
     In the two cases illustrated above, the two light guide material layers can be separately produced and arranged as plate elements adjacent to each other. 
     According to another appropriate embodiment of the invention, the display device can be provided with a reflector, reflecting the backlight and the sensor radiation, on the rear side of the lower light guide material layer facing away from the upper light guide material layer and/or a reflective coating, reflecting the backlight and the sensor radiation, on the rear side of the lower light guide material layer facing away from the upper light guide material layer. 
     In the aspect of the invention described before, a common reflector for both radiations (sensor radiation and backlight) is located on the rear side of the lower light guide material layer (i.e. the lower light guide plate element). However, a reflective layer can also additionally be arranged in the area between the two light guide plate elements, i.e. between the upper and the lower light guide material layer. However, this reflective coating is then selectively reflective, that is it reflects the radiation fed into the upper light guide plate element, while it is transmissive to radiation emitted from the lower light guide plate element. Thus, the reflector between the two plate elements is semi-transmissive. Such optical filters which are either reflective or transmissive depending on the wavelength are generally known. 
     The concept mentioned above can now be realized by the display device being provided with a reflector, reflecting the sensor radiation, on the rear side of the lower light guide material layer facing away from the upper light guide material layer or a reflective coating, reflecting the sensor radiation, on the rear side of the lower light guide material layer facing away from the upper light guide material layer, for example, wherein between the two light guide material layers a reflector reflecting the backlight and transmissive to the sensor radiation is arranged or on one of the two sides facing each other of the two light guide material layers a coating reflecting the backlight and transmissive to the sensor radiation is arranged. 
     Alternatively to what has been described before, the display device can also be provided with a reflector, reflecting the backlight, on the rear side of the lower light guide material layer facing away from the upper light guide material layer or a reflective coating, reflecting the backlight, on the rear side of the lower light guide material layer facing away from the upper light guide material layer, wherein between the two light guide material layers a reflector reflecting the sensor radiation and transmissive to the backlight is arranged or on one of the two sides facing each other of the two light guide material layers a coating reflecting the sensor radiation and transmissive to the backlight is arranged. 
     As far as a reflector is referred to above, this means an element provided in addition to the light guide plate and the light guide plate elements, respectively, and comprising a substrate with a corresponding coating, and a coating applied to the corresponding surface of the light guide plate and one of the light guide plate elements, respectively. 
     According to another variant, for achieving the aforementioned object, the invention further suggests a display device, in particular for a vehicle, comprising
         a display,   a backlighting unit for backlighting the display,   wherein the backlighting unit comprises a plurality of light sources for backlight and a light guide plate having a light emission side facing the display, an opposite rear side and a circumferential side edge surface arranged between the light emission side and the rear side,   wherein the light sources are arranged next to the light guide plate in a laterally offset manner for feeding light through at least a partial area of the side edge surface of the light guide plate into the latter, and backlight fed into the light guide plate from the side is emitted from the light emission side of the light guide plate, and   a proximity sensor system for sensing an object, such as a hand of a person, for example, located in the area in front of the display,   wherein the proximity sensor system comprises at least one proximity sensor system transmitter element for transmitting invisible sensor radiation, in particular IR sensor radiation, and at least one proximity sensor system receiver element for receiving sensor radiation reflected from an object in the area in front of the display,   wherein the at least one proximity sensor system transmitter element is arranged in a manner facing the rear side of the light guide plate and feeds sensor radiation into the light guide plate therethrough, and   a reflector reflecting the backlight and transmissive to the sensor radiation on the rear side of the light guide plate or a coating reflecting the backlight and transmissive to the sensor radiation on the rear side of the light guide plate,   wherein the at least one proximity sensor system receiver element is arranged inside the display and/or between the display and the light guide plate and/or behind the light guide plate.       

     In this variant of the invention, the proximity sensor system transmitter element(s) are arranged behind the light guide plate and thus face the rear side thereof via which they feed the sensor radiation into the light guide plate. 
     In this variant, too, it can appropriately be provided that the light guide plate comprises an upper light guide material layer having a circumferential upper side edge surface and a lower light guide material layer having a circumferential lower side edge surface, wherein the light sources feed backlight into at least a partial area of one, e.g. the upper, side edge surface and the at least one proximity sensor system transmitter element feeds sensor radiation into at least a partial area of the rear side of the lower light guide material layer facing away from the upper light guide material layer, and that between the two light guide material layers a reflector reflecting the backlight and transmissive to the sensor radiation is arranged or on one of the two sides facing each other of the two light guide material layers a coating reflecting the backlight and transmissive to the sensor radiation is arranged. 
     As explained above, the light guide plate has the characteristic of reflecting and scattering the fed radiation for allowing it to be emitted as homogeneously as possible from the light emission side. The measures required for reflecting and scattering are generally known and include provision of surface structures formed on at least one of the two main surfaces of the light guide plate and/or light-scattering particles or structures inside the light guide plate. 
     In addition, an optical diffuser can be arranged between the light emission side of the light guide plate and the display for further homogenizing the backlight and possibly the sensor radiation. 
    
    
     
       Hereunder the invention will be explained in detail on the basis of several exemplary embodiments with reference to the drawing in which: 
         FIG. 1  schematically shows the features of the setup of a display device essential to the invention according to a first exemplary embodiment, 
         FIG. 2  schematically shows the features of the setup of a display device essential to the invention according to a second exemplary embodiment, 
         FIG. 3  schematically shows the features of the setup of a display device essential to the invention according to a third exemplary embodiment, 
         FIG. 4  schematically shows the features of the setup of a display device essential to the invention according to a fourth exemplary embodiment, 
         FIG. 5  schematically shows the features of the setup of a display device essential to the invention according to a fifth exemplary embodiment, 
         FIG. 6  schematically shows the features of the setup of a display device essential to the invention according to a sixth exemplary embodiment, and 
         FIG. 7  schematically shows the features of the setup of a display device essential to the invention according to a seventh exemplary embodiment. 
     
    
    
       FIG. 1  schematically shows a first exemplary embodiment of a display device  10  with regard to the features essential to the invention. The display device  10  comprises a display  12  which is configured according to the LCD technology, for example. Other designs for optically representing characters, diagrams and the like are also possible. 
     The display  12  has a display side  14  as well as rear side  16  facing away from the former. Below the display  12  a backlighting unit  18  is located which comprises light sources  20  designed, according to the edge light concept, in the form of LEDs, for example, and arranged on a carrier strip  21  (e.g. rigid or flexible circuit board), and a light guide plate  22  as well as a reflector  24  located below the light guide plate  22 . Instead of the reflector  24 , the rear side  26  of the light guide plate  22  facing away from the display  12  can also be provided with a reflective coating. 
     On the light emission side  28  of the light guide plate  22  facing the display  12  that backlight (indicated by arrows  30 ) is emitted which is fed from the light sources  30  into the side edge surface  32  of the light guide plate  22 . 
     The display device  10  further comprises an optical proximity sensor system  34  which comprises one or a plurality of proximity sensor system transmitter elements  36  on the one hand as well as one or a plurality of proximity sensor system receiver elements  38 . These proximity sensor system receiver elements are either integrated in the display  12  or arranged behind the display  12 . The proximity sensor system transmitter elements  36  transmit sensor radiation in the invisible wavelength range (in the form of IR radiation, for example) which, like the backlight, is fed into the light guide plate  22  via the side edge surface  32  and, like the backlight  30 , is emitted from there by reflection and deflection from the light guide emission side  28  for traveling as sensor light (see arrows  40 ) into the area or the space in front of the light emission side  28  of the display  12 . An object located in the area or space, such as a hand or a finger of a hand of a person, is recognized by the sensor radiation  40  being reflected and received by one or a plurality of proximity sensor system receiver elements  38 . The evaluation of the signals supplied by the proximity sensor system receiver elements  38  is performed in an evaluation unit  42  which also controls the proximity sensor system transmitter elements  36 . By a corresponding sequential control of the proximity sensor system transmitter elements  36  and by knowing the location, i.e. the position of those proximity sensor system receiver elements  38  which receive or can receive the sequentially transmitted sensor radiation, an object above the display  12  or in front of the display  12  can be localized and approximately sensed with regard to its position, respectively. Hence, gesture recognition can be realized, for example. 
     In the first embodiment of the display device, thus the light sources  20  and the proximity sensor system transmitter elements  36  preferably configured as LEDs are located on the side of the light guide plate  22  and preferably along a plurality of side edges of the light guide plate  22 . Thus, it is not required that proximity sensor system transmitter elements or light sources are arranged below the light guide plate  22  such that the overall depth of the display device  10  is reduced. 
     In  FIG. 2  a second exemplary embodiment of a display device  110  is shown. When the elements shown correspond to those of the display device  10  of  FIG. 1  in terms of design or function, they are designated by reference numerals raised by 10. 
     In contrast to the display device  10 , in the display device  110  of  FIG. 2  the light sources  120  and the proximity sensor system transmitter elements  136  are arranged in two rows arranged one above the other on a carrier strip  121 . The light guide plate  122  is enlarged according to its height such that both radiation-transmitting elements, namely the light sources  120  and the proximity sensor system transmitter element  136  introduce radiation into the light guide plate  122  from the side via one of the side edge surfaces  132  or a plurality of side edge surfaces  132 . Otherwise, the setup of the display device  110  is similar to that of the display device  10 . 
     In  FIG. 3  the general setup of a third embodiment of a display device  210  is schematically shown. In  FIG. 2  those elements which have the same functions as or are identical with the display device elements of  FIG. 2  are designated by reference numerals raised by 200. 
     As in the exemplary embodiment of the display device  110  of  FIG. 2 , in the display device  210  of  FIG. 3 , too, the elements transmitting radiation, namely the light sources  220  and the proximity sensor system transmitter elements  236  are arranged in two rows arranged one above the other on the carrier strip  221 . In contrast to the display devices  10  and  110 , the light guide plate  222  is configured as two light guide plate elements  222   a  and  222   b  arranged one above the other. Each one of these light guide plate elements  222   a ,  222   b  receives radiation either from the light sources  220  or the proximity sensor system transmitter elements  236 . The radiation of the light sources  220 , i.e. the backlight, travels into the side edge surface  232   a  of the upper (in  FIG. 3 ) light guide plate element  222   a , while the IR sensor radiation of the proximity sensor system transmitter elements  236  travels into the side edge surface  232   b  of the lower light guide plate element  222   b . Below the bipartite light guide plate  222  a reflector  224  is located, or the lower side of the lower light guide plate element  222   b  is provided with a coating having reflection properties. The division of the light guide plate  222  into the two light guide plate elements  222   a  and  222   b  allows for ensuring that the optical properties can be adapted to the respective radiation (backlight and sensor radiation, respectively) and thus optimized by the selection of the light guide materials and their configuration. 
       FIG. 4  shows an embodiment of a display device  310  where, again, those elements which are similar to or identical with the elements of the display device  210  are designated by reference numerals raised by 100. 
     The difference between the display device  310  and that of  FIG. 3  is the additional arrangement of a semitransmissive reflector  344  and a semitransmissive coating, respectively, arranged between the two light guide plate elements  322   a  and  322   b . This semitransparent reflector  344  and this semitransparent coating, respectively, which is either arranged on the lower side of the upper light guide plate element  322   a  or on the upper side of the lower light guide plate element  322   b  reflects only the backlight fed into the upper light guide plate element  322   a , while it is transmissive to the sensor radiation emitted from the lower light guide plate element  322   b.    
     In  FIGS. 5 and 6  two exemplary embodiments of display devices  410  and  510 , respectively, are shown where, in contrast to the exemplary embodiments of  FIGS. 1 to 4 , the proximity sensor system transmitter elements are arranged below the light guide plate. Here, again, those components of the display device  410  which have the same functions and design as those of the display device  10  of  FIG. 1  are designated by reference numerals raised by 400. 
     On the lower side of the light guide plate  422  a semitransmissive reflector  444  or a semitransmissive reflective coating, respectively, reflecting the backlight (see arrows  430 ) of the light sources  420  towards the light emission side of the light guide plate  422  on the one hand and being transmissive to the sensor radiation coming from below (see arrows  440 ) is arranged. 
     The display device  510  of  FIG. 6 , in contrast to the display device  410  of  FIG. 5 , additionally comprises another light guide plate element  522   b  below the semitransmissive reflector  544 , which, together with the light guide plate element  522   a  used for distributing the backlight, forms the light guide plate  522 . 
     It should be appreciated that the arrangement of the light sources and the proximity sensor system transmitter elements can be vice versa as compared to the situation shown in  FIGS. 5 and 6 . The backlight sources can hence be arranged below the light guide plate or the assembly of the two light guide plate elements, respectively, while the proximity sensor system transmitter elements are located on the side of the light guide plate and on the side of one of the light guide plate elements, respectively. 
     As described above, in all exemplary embodiments of the display devices  10 ,  110 ,  210 ,  310 ,  410  and  510  described here, the light guide plates and the light guide plate elements, respectively, ensure a homogenization of the radiation emitted by them. This is realized by means of measures, generally known in prior art, for scattering and/or reflecting due to internal reflections inside the light guide plates. For further homogenization of the emitted radiation, a diffuser can be arranged between the light guide plates and the display, as is exemplified in  FIG. 7  on the basis of the display device  610  (see diffuser  646 ). 
     Further, in each display or in each exemplary embodiment of the display device a touch sensor system is appropriately integrated which is not shown in the Figures for the sake of clarity. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  Display device 
           12  Display 
           14  Display side of the display 
           16  Rear side of the display 
           18  Backlighting unit 
           20  Light sources 
           21  Carrier strip 
           22  Light guide plate 
           24  Reflector 
           26  Rear side of the light guide plate 
           28  Light emission side of the light guide plate 
           30  Backlight 
           32  Side edge surface of the light guide plate 
           34  Proximity sensor system 
           36  Proximity sensor system transmitter elements 
           38  Proximity sensor system receiver elements 
           40  Sensor radiation 
           42  Evaluation unit 
           110  Display device 
           112  Display 
           114  Display side of the display 
           116  Rear side of the display 
           118  Backlighting unit 
           120  Light sources 
           121  Carrier strip 
           122  Light guide plate 
           124  Reflector 
           126  Rear side of the light guide plate 
           128  Light emission side of the light guide plate 
           130  Backlight 
           132  Side edge surface of the light guide plate 
           134  Proximity sensor system 
           136  Proximity sensor system transmitter elements 
           138  Proximity sensor system receiver elements 
           140  Sensor radiation 
           142  Evaluation unit 
           210  Display device 
           212  Display 
           214  Display side of the display 
           216  Rear side of the display 
           218  Backlighting unit 
           220  Light sources 
           221  Carrier strip 
           222   a  Upper light guide plate elements 
           222   b  Lower light guide plate elements 
           224  Reflector 
           226  Rear side of the light guide plate 
           228  Light emission side of the light guide plate 
           230  Backlight 
           232   a  Side edge surface of the upper light guide plate elements 
           232   b  Side edge surface of the lower light guide plate elements 
           234  Proximity sensor system 
           236  Proximity sensor system transmitter elements 
           238  Proximity sensor system receiver elements 
           240  Sensor radiation 
           242  Evaluation unit 
           310  Display device 
           312  Display 
           314  Display side of the display 
           316  Rear side of the display 
           318  Backlighting unit 
           320  Light sources 
           321  Carrier strip 
           322   a  Upper light guide plate elements 
           322   b  Lower light guide plate elements 
           324  Reflector 
           326  Rear side of the light guide plate 
           328  Light emission side of the light guide plate 
           330  Backlight 
           332   a  Side edge surface of the upper light guide plate elements 
           332   b  Side edge surface of the lower light guide plate elements 
           334  Proximity sensor system 
           336  Proximity sensor system transmitter elements 
           338  Proximity sensor system receiver elements 
           340  Sensor radiation 
           342  Evaluation unit 
           344  Reflector 
           410  Display device 
           412  Display 
           414  Display side of the display 
           416  Rear side of the display 
           418  Backlighting unit 
           420  Light sources 
           421  Carrier strip 
           422  Light guide plate 
           424  Reflector 
           426  Rear side of the light guide plate 
           428  Light emission side of the light guide plate 
           430  Backlight 
           432  Side edge surface of the light guide plate 
           434  Proximity sensor system 
           436  Proximity sensor system transmitter elements 
           438  Proximity sensor system receiver elements 
           440  Sensor radiation 
           442  Evaluation unit 
           444  Reflector 
           510  Display device 
           512  Display 
           514  Display side of the display 
           516  Rear side of the display 
           518  Backlighting unit 
           520  Light sources 
           521  Carrier strip 
           522   a  Upper light guide plate 
           522   b  Lower light guide plate 
           524  Reflector 
           526  Rear side of the light guide plate 
           528  Light emission side of the light guide plate 
           530  Backlight 
           532  Side edge surface of the light guide plate 
           534  Proximity sensor system 
           536  Proximity sensor system transmitter elements 
           538  Proximity sensor system receiver elements 
           540  Sensor radiation 
           542  Evaluation unit 
           544  Reflector 
           610  Display device 
           612  Display 
           614  Display side of the display 
           616  Rear side of the display 
           618  Backlighting unit 
           620  Light sources 
           621  Carrier strip 
           622   a  Upper light guide plate 
           622   b  Lower light guide plate 
           624  Reflector 
           626  Rear side of the light guide plate 
           628  Light emission side of the light guide plate 
           630  Backlight 
           632   a  Side edge surface of the upper light guide plate elements 
           632   b  Side edge surface of the lower light guide plate elements 
           634  Proximity sensor system 
           636  Proximity sensor system transmitter elements 
           638  Proximity sensor system receiver elements 
           640  Sensor radiation 
           642  Evaluation unit 
           644  Reflector 
           646  Diffuser