Patent Publication Number: US-2022229292-A1

Title: Heads up display with textured surface

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 63/138,000 filed on Jan. 15, 2021, the disclosure of which is hereby incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a heads-up display (HUD) having a component therein provided with a textured surface. 
     BACKGROUND 
     Various automotive vehicles have a heads-up display (HUD) system. In a HUD system, a light source projects a light, which is reflected onto a windshield of the vehicle. The focal point of the light is out beyond the vehicle, enabling the driver of the vehicle to view the light on the windshield without changing focus while looking at the outside environment. 
     SUMMARY 
     In an embodiment, a heads-up display (HUD) assembly for a vehicle includes a first reflective polarizer subassembly and a second reflective polarizer subassembly. The first reflective polarizer subassembly includes a first clear substrate having an upper surface and a lower surface, and a first polarizing film bonded to the upper surface of the first clear substrate. The second reflective polarizer subassembly includes a second clear substrate having an upper surface and a lower surface, and a second polarizing film bonded to the upper surface of the second clear substrate. A thin-film transistor (TFT) panel is disposed between the lower surface of the first clear substrate and the upper surface of the second clear substrate. At least one of the lower surface of the first clear substrate and the upper surface of the second clear substrate is textured. 
     In an embodiment, a heads-up display (HUD) assembly includes a thin-film transistor (TFT) panel, and a reflective polarizer subassembly having a surface contacting the TFT panel in a face-to-face relationship. The surface of the reflective polarizer subassembly that contacts the TFT panel is textured. 
     In an embodiment, a thin-film transistor (TFT) subassembly for a heads-up display (HUD) includes a TFT panel having an upper surface and a lower surface, as well as a first reflective polarizer subassembly. The first reflective polarizer subassembly has a first clear substrate having a lower surface and an upper surface, and a first polarizing film laminated to the upper surface of the first clear substrate. The lower surface of the first clear substrate is textured and attached to the upper surface of the TFT panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side schematic view of a HUD system, according to an embodiment. 
         FIG. 2  illustrates an exploded perspective view of a HUD assembly, according to an embodiment. 
         FIG. 3  illustrates a cross-sectional view of a HUD assembly, according to an embodiment. 
         FIG. 4  is an enlarged view of a portion of  FIG. 3  and illustrates a cross-section of a reflective polarizer sub-assembly, according to an embodiment. 
         FIG. 5  is an enlarged view of a portion of  FIG. 4  illustrating a textured surface on one of the layers of material of the reflective polarizer sub-assembly, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     A heads-up display (HUD), also referred to as a head-up display, is a type of transparent display that presents data without requiring the user to look away from the usual environment. In vehicular applications, data can be presented on the windshield (for example), in a transparent and visually-unobstructed manner so that the driver can clearly see the surrounding environment while driving. Some data available for display on the windshield includes vehicle speed, turn-by-turn navigation instructions, warnings regarding surrounding objects, etc. 
       FIG. 1  illustrates a general HUD system  10  according to one embodiment. The HUD system  10  is in a passenger vehicle, such as a car, truck, sports utility vehicle, van, and the like. In other embodiments, the HUD system  10  can be implemented in aviation, military, and other applications. The HUD system  10  includes various components beneath the dashboard of the vehicle. For example, the HUD system  10  can include a projector unit  12 . For simplicity sake, the projector unit  12  is shown herein to have a light source  14 , which can be a light-emitting diode (LED) light source located at the rear of the projector unit  12 , for example. Light transmitted from the light source  14  is generally shown at  16 . The light from the light source  14  is sent to a screen or visual display, such as thin-film transistor (TFT) or a reflective polarizer sub-assembly, in an embodiment. The TFT can create an image, and the LEDs can light up the image; in other words, the LEDs can be a backlight for the TFT. The light can then be reflected off of a mirror  18 . The light reflected off of the mirror  18 , shown generally at  20 , passes through an aperture or transparent region of the dashboard and is reflected off the vehicle windshield  22  to the driver  26 . The light shown on the windshield can be shown over an area  24  of the windshield that can, for example, overlay with the road ahead of the driver  26  from the driver&#39;s viewpoint. 
     It should be understood that  FIG. 1  is a simplified view of an HUD system  10 . As will be described below, the TFT (or, generally, the mirror  18 ) can be a subassembly of various structures, and is herein described as a reflective polarizer subassembly in various embodiments. Also, while not shown in  FIG. 1 , the HUD system  10  can include many other components to aid in the effective delivery of light to the windshield, such as collimators, lenses, additional mirrors, and other structure. While the HUD system  10  may include TFT, other screens or visual displays may be used, such as a liquid crystal display (LCD), liquid crystal on silicon (LCoS), digital micro-mirrors (DMDs), organic light-emitting diodes (OLEDs), or others made using a wide variety of semiconductor materials (e.g., silicon, glass, cadmium selenide, metal oxides, etc.) which is illuminated by the light from the light source as the light as it is projected to the windshield. 
     A reflective polarizer may be used to prevent sunlight from damaging the TFT surface. In the context of a HUD system, this reflective polarizer may be a thin film that is laminated to a clear substrate which is, in turn, installed on the TFT surface so that the clear substrate and the TFT touch. When the clear substrate touches the TFT, the two parts can undesirably and accidentally bond to each other to form surface tension, which can result in optical defects. 
     According to various embodiments described herein, one side of the clear substrate can be textured. The texturing of the clear substrate can inhibit the clear substrate from bonding with the TFT, thus preventing any accidental optical defects. As will be described herein, the texturing of the surface can be accomplished via surface roughness, frosting, or the like that roughens the surface enough without distorting the image displayed. 
       FIG. 2  illustrates an exploded perspective view of an HUD assembly  30  according to an embodiment.  FIG. 3  illustrates a cross-sectional view of a similar HUD assembly  30 . The only differences between the views shown in  FIG. 2  and  FIG. 3  are in the overall shapes and inclusion of certain structure, and therefore similar reference numbers are used in both figures. Referring to  FIGS. 2-3 , the HUD assembly  30  includes a case  32 , also referred to as an outer housing or assembly case. The TFT panel  34  may be a metal-oxide-semiconductor field-effect transistor (MOSFET), for example, which may be made by depositing thin films of an active semiconductor layer and a dielectric layer and metallic contacts over a supporting substrate (e.g., glass, etc.) The case  32  may support a TFT screen or TFT panel  34 . The TFT panel  34  is also assembled to a cover  36  which has a central opening  38  aligned with the TFT panel  34  such that the illumination of the TFT panel  34  is visible through the opening  38 . The orientation and positioning of the HUD assembly  30  can be such that the TFT panel  34  is directly aligned with an opening in the dashboard of the vehicle. 
     The HUD assembly  30  may also include a light source  40 , such as one described above. In the illustrated embodiment, the light source  40  is an LED board, e.g., a printed circuit board (PCB)  41  with LEDs  43  arranged thereon. A first optical lens  42  including a plurality of individual lenses arranged on a lens board are also provided, with each lens aligned with a respective one of the LEDs, for example. A second optical lens  44  is also provided, spaced apart from the first optical lens  42 . A lens spacer  46  may be provided, attached to both lenses  42 ,  44  and configured to maintain a spatial relationship between the lenses. 
     The HUD assembly  30  may also be provided with a heat sink  50  at a rear of the assembly, which is illustrated in the embodiment of  FIG. 2 . The heat sink  50  can be attached directly to the case  32 , for example. A plurality of fasteners (e.g., screws, bolts, etc.)  52  can extend through apertures formed in the heat sink  50  to connect to corresponding holes in the board of the light source  40  to connect the two. The heat sink  50  may be provided with fins  54  for dispersion of heat. Similarly, the case  32  may be provided with fins  56  for dispersion of heat. 
     The HUD assembly  30  also includes at least one reflective polarizer subassembly. In the illustrated embodiments of  FIG. 2  and  FIG. 3 , there are two reflective polarizer subassemblies, namely a first reflective polarizer subassembly  60  and a second reflective polarizer subassembly  62 . But, it should be understood that the teachings provided herein can be applied to a HUD system in which only a single reflective polarizer subassembly is provided, e.g., on only one side of the TFT panel  34 . 
     In the illustrated embodiment, a TFT sandwich is created with the TFT panel  34  in between and directly contacting the first polarizer subassembly  60  and the second polarizer subassembly  62 . The first polarizer subassembly  60  is configured to keep sunlight from shining on the TFT panel  34 , while the second polarizer subassembly  62  is configured to reflect some light from the light source  40  away from the TFT panel  34  to prevent the TFT panel  34  from overheating. 
     In an embodiment, the second polarizer subassembly  62  does not directly contact the case  32 . Instead, a piece of foam  63  or other insulative material may be provided between the second polarizer subassembly  62  and the case. The foam  63  may be placed at various spaced-apart locations about the perimeter along one side of the second polarizer subassembly, for example. 
       FIG. 4  illustrates an enlarged view of the TFT sandwich, namely the TFT panel  34  between the first polarizer subassembly  60  and the second polarizer subassembly  62 . This can also be referred to as a TFT subassembly.  FIG. 5  is an enlarged view of a side of the polarizer subassemblies that faces and directly contacts the TFT panel  34 .  FIG. 5  is an enlarged view of an upper surface of the second polarizer subassembly, but the surface features described herein can also be present on the lower of the first subassembly  60 . In other words, the surface features described herein can be on both polarizer subassemblies  60 ,  62  on a respective surface thereof that contacts the TFT panel  34 . 
     Each reflective polarizer subassembly includes a polarizing film connected to a clear substrate. In particular, the first polarizer subassembly  60  includes a first clear substrate  64  and a first polarizing film  66 , and the second polarizer subassembly  62  includes a second clear substrate  74  and a second polarizing film  76 . The first clear substrate  64  and second clear substrate  74  may be polymethyl methacrylate (PMMA), also referred to as acrylic, acrylic glass, or plexiglass. The first polarizing film  66  and the second polarizing film  76  may be a film reflective polarizer (FRP) or other similar polarizing film that is laminated to the respective clear substrate. Each polarizing film  66 ,  76  may itself include multiple layers of films, although only a single layer is shown in the illustrated embodiment. The polarizing films  66 ,  76  are may include a combination of polymer and multilayer film technology configured to recycle some of the rejected polarization to increase light output. In particular, the polarizing films  66 ,  76  may reflect one plane of light polarization and transmit or reflect the other. 
     The first clear substrate  64  has a lower surface  67  and an opposing upper surface  68 . The lower surface  67 , when assembled to the TFT panel  34 , directly contacts an upper surface  35  of the TFT panel  34 . In other embodiments, there is an air gap between the lower surface  67  and the upper surface  35 . The upper surface  68  of the first clear substrate  64  is covered by the first polarizing film  66 , which can be laminated thereto. 
     The second clear substrate  74  has an upper surface  77  and an opposing lower surface  78 . The upper surface  77 , when assembled to the TFT panel  34 , directly contacts a lower surface  37  of the TFT panel  37 . In other embodiments, there is an air gap between the upper surface  77  and the lower surface  37 . The lower surface  78  of the second clear substrate  74  is covered by the second polarizing film  76 , which can be laminated thereto. 
     As explained above, optical defects in the output of the HUD system  10  are undesirable, and might derive from accidentally bonding between the lower surface  67  of the first clear substrate  64  and the upper surface  35  of the TFT panel  34 , and/or from accidental bonding between the upper surface  77  of the second clear substrate  74  and the lower surface  37  of the TFT panel  34 . Therefore, as disclosed herein, the lower surface  67  and/or the upper surface  77  may be textured or roughened to inhibit these accidental bonds. This is represented by the roughened surface features shown in  FIG. 4 . 
       FIG. 5  is an enlarged view of the upper surface  77  of the second clear substrate  74 , illustrating one example of surface features  80  formed thereon. It should be understood that the described surface features  80  may also be provided on the lower surface  67  of the first clear substrate  64 . 
     The surface features  80  may be undulations, ridges, bumps, humps, etches, scratches, or the like that are configured to roughen the upper surface  77 . The surface features  80  may be the result of frosting the upper surface  77  such that the upper surface is a frosted surface, for example. Glass-etching cream or other similar abrasive materials can be used to roughen the upper surface  77  and create the surface features  80 . In yet other embodiments, the surface features  80  are formed from polishing such as tape polishing, abrasive polishing, chemical mechanical polishing (CMP), or the like. In other embodiments, a texture is etched onto surfaces of the mold (e.g., glass) that are used to mold the clear substrates  64 ,  74 , so that the texture is applied to the clear substrates  64 ,  74  during formation similar to applying texture onto injection molded parts. The upper surface  77  can therefore be referred to as an etched surface, a frosted surface, a textured surface, an uneven surface, or the like. 
     The textured surface described herein prevents bonding or adhesion between the TFT panel  34  and either or both of the clear substrates  64 ,  74 . By texturing or roughening the surface of the clear substrate  64 ,  74  that comes in contact with the TFT panel  34 , image distortion resulting from accidental bonding is removed while the clarity, intensity, evenness, and sharpness of the displayed image output by the HUD system  10  is not noticeably impacted. 
     While references herein are made to “upper” and “lower” surfaces of the various components, it should be understood that these are merely referring to the orientation shown in the figures. These terms are not to be limiting to the actual orientation of the product in production, but merely refer to the orientation shown in the figures. For example, while it has been described that the lower surface  67  of the clear substrate  64  is textured, and the upper surface  77  of the clear substrate  74  is textured, it can alternatively be stated that each clear substrate has opposing first and second surfaces, and one of the surfaces is textured. The other of the two opposing surfaces may not be textured, e.g., may be smooth, clear, and free from any ridges, etches or other purposefully-manufactured surface features. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.