Patent Publication Number: US-2019187357-A1

Title: Light guide structure having light trap section

Description:
TECHNICAL FIELD 
     The present disclosure relates to a light guide structure which includes a light trap section. 
     BACKGROUND 
     An instrument cluster provided within automobiles generally include illuminated indicating devices for displaying vehicle information such as vehicle speed, fuel level, or headlamp status. Typically such illuminated indicating devices include a display surface, a light source, and a light guide disposed between the display surface and the light source. The display surface is generally provided with indicia corresponding to vehicle information, and such indicia are illuminated with light output from the light source and carried by the light guide. 
     SUMMARY 
     According to an aspect of the present disclosure, at least two light guides, each of which is configured to guide light therein, are integrally connected to each other through a bridge to form a light guide structure. The bridge includes a light trap section configured to block a substantial amount of light from passing therethrough. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a light guide structure. 
         FIG. 2  is an exploded view of an illuminated indicating device. 
         FIG. 3  is a cross section view of a light guide structure. 
         FIG. 4  is a schematic view of a bridge. 
         FIG. 5A  is an optic ray simulation view of a comparative example. 
         FIG. 5B  is an optic ray simulation of a bridge. 
         FIG. 5C  is an optic ray simulation of a bridge. 
         FIG. 6  is a cross section view of a light guide structure. 
         FIG. 7  is a schematic view of a bridge. 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
       FIG. 1  is a plan view of a light guide structure  10  according to a first embodiment of the present disclosure. It should be noted that the specific shape of the light guide structure  10  shown in  FIG. 1  is exemplary in nature and is not intended to be limiting. As will become clear in the following explanations, the shape and size of the light guide structure  10  may be modified as appropriate based on specific applications. The light guide structure  10  is an optical prism configured to guide light. In the present embodiment, the light guide structure  10  is an acrylic prism. In alternative embodiments, the light guide structure  10  may be formed of other types of transparent materials, including resin or other plastics. 
     As illustrated in  FIG. 1 , the light guide structure  10  includes a first light guide  12 , a second light guide  14 , and a bridge  16  which connects the first light guide  12  with the second light guide  14 . The first light guide  12 , the second light guide  14 , and the bridge  16  are integrally formed with each other, for example by injection molding or casting. 
     The light guide structure  10  is configured to be mounted in an illuminated indicating device  1 , as illustrated in  FIG. 2 . The illuminated indicating device  1  may be, for example, part of a vehicular instrument cluster. The light guide structure  10  is disposed between a display surface  20  and a light source  30 . In the illustrated embodiment, the display surface  20  is a front panel of the illuminated indicating device  1 , and includes display indicia  22 ,  24 . The display indicia  22 ,  24  are formed at locations corresponding to the locations of the first light guide  12  and the second light guide  14 . Further, in the illustrated embodiment, the light source  30  is a circuit substrate, on which a variety of electrical components are mounted, including light emitting diodes (LEDs)  32 ,  34 . The LEDs  32 ,  34  are also disposed at locations corresponding to the locations of the first light guide  12  and the second light guide  14 . 
     A support structure  40  may be disposed in between the light guide structure  10  and the light source  30 . In the illustrated embodiment, the support structure  40  is provided with mounting holes for positioning the light guide structure  10  with respect to the display surface  20  and the light source  30 . However, in alternative embodiments, the support structure  40  does not need to be separately provided, and may be integrally formed with, for example, the display surface  20  or the light source  30 . 
     The light guide structure  10  is configured to guide light from the LEDs  32 ,  34  of the light source  30  to the display indicia  22 ,  24  of the display surface  20 . As a result, the display indicia  22 ,  24  may be illuminated by light emitted from the LEDs  32 ,  34 . Then, by selectively powering on and off the LEDs  32 ,  34 , the display indicia  22 ,  24  may be selectively illuminated to convey vehicle operational information to a passenger. 
     As shown in  FIG. 3 , the first light guide  12  includes a first input face  121  which faces the LED  32 , and includes a first output face  122  on the opposite end from the first input face  121 . The first output face  122  is positioned to face the display indicia  22  (see  FIG. 2 ). In this regard, the light guide structure  10  is provided such that light emitted from the LED  32  enters the first input face  121  and exits out of the first output face  122  to illuminate the display indicia  22 . 
     In the present embodiment, the output side of the light guide structure  10  (i.e., the surface shown in  FIG. 1 ) is formed as a flat plate member. As a result, in practice, the entire output surface shown in  FIG. 1  may be illuminated to some extent when the light guide structure  10  is outputting light, due to the integral formation of the light guide structure  10 . Accordingly, there is no clear physical delineation with respect to the boundaries of the first output face  122 . Instead, as shown by a dotted circle in  FIGS. 1 and 2 , the first output face  122  generally refers to a portion of the surface of the light guide structure  10  that corresponds to the position of the first input face  121  and therefore outputs the majority of the light guided from the first input face  121 . 
     The second light guide  14  is positioned in a similar manner with respect to the LED  34 . Specifically, the second light guide  14  similarly includes a second input face  141  which faces the LED  34 , and includes a second output face  142  on the opposite end from the second input face  141 . The second output face  142  is positioned to face the display indicia  24  (see  FIG. 2 ). In this regard, the light guide structure  10  is provided such that light emitted from the LED  34  enters the second input face  141  and exits out of the second output face  142  to illuminate the display indicia  24 . 
     In addition, similar to the first output face  122 , the second output face  142  also generally refers to a portion of the surface of the light guide structure  10  that corresponds to the position of the second input face  141  and therefore outputs the majority of the light guided from the second input face  141 . 
     The illustrated shape of the light guide structure  10  is not intended to be limiting with respect to the first input face  121 , the first output face  122 , the second input face  141 , or the second output face  142 . For example, in an alternate embodiment, the first output face  122  and/or the second output face  142  may be formed as a protrusion and thus have a clearly delineated shape. 
     The shapes and sizes of the first light guide  12  and the second light guide  14  are not necessarily the same, and may be modified as appropriate based on the desired application. In addition, the exemplary shapes of the first light guide  12  and the second light guide  14  in the figures are not intended to be limiting. For instance, while  FIG. 3  illustrates a tapered shape, the first light guide  12  or the second light guide  14  may be formed in a variety of geometric and non-geometric shapes, such as rectangular prisms, oblique prisms, or irregular polyhedrons as long as light is guided from the light source  30  to the display surface  20 . 
     In order to guide light, light may be entirely or mostly prevented from exiting the side walls of the first light guide  12  and the second light guide  14  by relying on the phenomenon of total internal reflection, which causes light to be entirely reflected by the side walls of the first light guide  12  and the second light guide  14  over a particular range of angles. Additional processing may be performed on the side walls of the first light guide  12  and the second light guide  14  to further prevent light from exiting from the side walls, such as coating the outside of the side walls with a reflective material, e.g., through aluminum sputtering. As a result, light may be reliably guided from the first input face  121  to the first output face  122  in the first light guide  12 , and from the second input face  141  to the second output face  142  in the second light guide  14 . 
     The bridge  16 , which connects the first light guide  12  with the second light guide  14 , is integrally formed with the first light guide  12  and the second light guide  14  from the same material, e.g., acrylic. In other words, there is no physical medium boundary between the bridge  16 , the first light guide  12 , and the second light guide  14 . As such, the phenomenon of total internal reflection would not occur at the connection portions between the bridge  16 , the first light guide  12 , and the second light guide  14 . In addition, due to the integral forming, it is not physically possible to apply a reflective material between the bridge  16  and the first light guide  12  or the second light guide  14 . As a result, light within the light guide structure  10  may freely cross the boundaries between the first light guide  12 , the second light guide  14 , and the bridge  16 . 
     In addition, since the bridge  16  is integrally formed with the first light guide  12  and the second light guide  14  from the same material as a monolithic entity, there is no physical delineation between these elements, and so it is not possible to identify a non-arbitrary boundary between these elements. In this regard, labels such as “light guide” as used herein are not intended to refer to exact portions of the light guide structure  10 , but rather general areas as defined by their functions and well understood by a skilled artisan. 
     Next, the structural configuration of the bridge  16  will be described. As outlined in  FIG. 3 , the bridge  16  includes a first end  161  connected to the first light guide  12 , a second end  162  connected to the second light guide  14 , and a light trap section  163  formed between the first end  161  and the second end  162 . Similar to the overall light guide structure  10 , since the bridge  16  itself is also an integrally formed prism, there is no physical delineation between the first end  161 , the second end  162 , and the light trap section  163 . Accordingly, in this case as well, labels such as “first end” as used herein are not intended to refer to exact portions of the bridge  16 , but rather general areas as defined by their functions. 
     The bridge  16  is connected to the first light guide  12  and the second light guide  14  in a manner so as to not interfere with the light guiding faces of the first light guide  12  and the second light guide  14 . For example, the first end  161  of the bridge  16  may be connected to the first light guide  12  between the first input face  121  and the first output face  122 . Further, the second end  162  of the bridge  16  may be connected to the second light guide  14  between the second input face  141  and the second output face  142 . 
       FIG. 4  shows a detailed schematic view of the bridge  16  and its light trap section  163 . As illustrated, the light trap section  163  is formed by an inwardly V-shaped wall section  164  and an outwardly V-shaped wall section  165  on opposing sides from each other. In other words, the inwardly V-shaped wall section  164  and the outwardly V-shaped wall section  165  face each other. The inwardly V-shaped wall section  164  is configured with a V-angle A 1  which is greater than a V-angle A 2  of the outwardly V-shaped wall section  165 . The remaining wall sections of the light trap section  163 , i.e., those connecting the inwardly V-shaped wall section  164  with the outwardly V-shaped wall section  165 , are preferably simple flat walls as illustrated in  FIG. 1 . 
     The inwardly V-shaped wall section  164  includes a pair of inwardly angled surfaces  164   a,    164   b  which are angled toward the inside of the light trap section  163  (i.e., formed as a depression) and which connect to each other at an inner vertex V 1 . In other words, the pair of inwardly angled surfaces  164   a,    164   b  are angled toward the inner vertex V 1 . The V-angle A 1  is defined as a minimum positive angle between the pair of inwardly angled surfaces  164   a,    164   b.  Similarly, the outwardly V-shaped wall section  165  includes a pair of outwardly angled surfaces  165   a,    165   b  which are angled away from the inside of the light trap section  163  (i.e., formed as a protrusion) and which connect to each other at an outer vertex V 2 . In other words, the pair of outwardly angled surfaces  165   a,    165   b  are angled toward the outer vertex V 2 . The V-angle A 2  is defined as a minimum positive angle between the pair of outwardly angled surfaces  165   a,    165   b.    
     As illustrated in  FIG. 4 , the inner vertex V 1  is positioned closer to the outer vertex V 2  than the first end  161  and the second end  162  are to the outer vertex V 2  by a margin X in a direction from the inner vertex V 1  to the outer vertex V 2 . In other words, the pair of inwardly angled surfaces  164   a,    164   b  block a direct path for light from the first end  161  to the second end  162 , since the pair of inwardly angled surfaces  164   a,    164   b  connect to each other at the inner vertex V 1 . While  FIG. 4  illustrates sharp angles near the vertices V 1 , V 2 , in practice, due to manufacturing constraints etc., the light trap section  163  may be slightly curved at the vertices V 1 , V 2 . 
     In the present embodiment, the V-angle A 1  of the inwardly V-shaped wall section  164  is preferably between 110 degrees and 130 degrees, and more preferably between 115 and 125 degrees. In one preferred embodiment, the V-angle A 1  is 120 degrees. Further in the present embodiment, the V-angle A 2  of the outwardly V-shaped wall section  165  is preferably between 80 and 100 degrees, and more preferably between 85 and 95 degrees. In one preferred embodiment, the V-angle A 2  is 90 degrees. Further, as a skilled artisan would readily appreciate, these angle values are not intended to be exact, and are intended to include slight variations which may be caused by a number of factors such as tolerance during manufacturing, minor deformations during transport, storage, or use, etc. 
     Next an operational effect of the bridge  16  according the present embodiment will be explained with reference to  FIGS. 5A to 5C , which are optic ray simulations assuming perfectly reflective surfaces arranged in a manner analogous to the bridge  16  of the present embodiment. 
     As described previously, since the bridge  16  is integrally formed with the first light guide  12  and the second light guide  14 , light is free to travel through any arbitrary boundary between these elements. In this case, there is a concern that light from the first light guide  12  may inadvertently travel through the bridge  16  and leak into the second light guide  14 , or conversely leak from the second light guide  14  into the first light guide  12 . Such a light leak may result in an unintended illumination of the indicia  22 ,  24  in the illuminated indicating device  1 . However, with the configuration of the light guide structure  10  described in the present embodiment, the light trap section  163  of the bridge  16  may prevent most or substantially all light from leaking between the first light guide  12  and the second light guide  14 . 
     First, a comparative example is shown in  FIG. 5A . In the comparative example, there is no direct path for light to travel through the bridge, similar to the present embodiment. However, contrary to the bridge  16  of the present embodiment, the comparative example in  FIG. 5A  is formed with equal V-angles A 1 , A 2  each set at 120 degrees. In this case, assuming a beam light source on the right hand side, nearly all of the emitted light rays still pass through the comparative example due to reflection. In other words, if light from either one of the first light guide  12  and the second light guide  14  enters the comparative example structure, a large portion of that light may then leak through to the other one of the first light guide  12  and the second light guide  14 . This leaked light may then result in unintended illuminations. 
     In contrast,  FIG. 5B  shows a bridge structure that satisfies the relationship A 1 &gt;A 2  with the preferred values of A 1  being 120 degrees and A 2  being 90 degrees. In this case, assuming a beam light source on the right hand side, most or substantially all light rays are reflected back toward the right hand side. In other words, according to the present embodiment, even if light from either one of the first light guide  12  and the second light guide  14  enters the bridge  16 , very little to no light leaks through to the other one of the first light guide  12  and the second light guide  14 . 
       FIG. 5C  is provided for completeness and illustrates the same situation as  FIG. 5B  except with a point light source on the right hand side instead of a beam light source. Even in this case, as shown, substantially all light rays are reflected back toward the right hand side. 
     It should be noted that the diagrams of  FIGS. 5A to 5C  are simplifications and in practice, it is unlikely that all light rays in all situations are completely blocked by the light trap section  163 . This is because of a variety of factors, including light rays which may enter the bridge  16  at extreme angles to bypass the light trap section  163 , manufacturing imperfections causing unpredictable or incomplete reflections at some parts, and other uncontrollable factors. As such, it is not the intention of the present disclosure to provide a bridge  16  capable of blocking all light from passing therethrough. Rather, it is sufficient as long as the bridge  16  is capable of blocking a sufficient portion of leaked light such that any unintended illumination caused by the leaked light is not easily noticed by a user. 
     To further reduce light leak, the bridge  16  itself may be treated to prevent light from escaping through its side walls (e.g., the inwardly V-shaped wall section  164  or the outwardly V-shaped wall section  165 ). For example, the outside of the bridge  16  may also be treated with a reflective material, e.g., through aluminum sputtering. This ensures that light within the bridge  16  is properly reflected. 
     The light guide structure  10  according to the present embodiment exhibits a number of technical advantages. 
     According to the present embodiment, the bridge  16  is integrally formed with the first light guide  12  and the second light guide  14 . In other words, the first light guide  12  and the second light guide  14  are provided together as a single component as the light guide structure  10 . In this case, the light guide structure  10  may be manufactured in a simple and quick manner, i.e., through injection molding, rather than manufacturing each light guide  12 ,  14  separately. This advantage is especially pronounced when applied to a vehicle instrument panel such as the illuminated indicating device  1 . As shown in  FIG. 2  for example, a large number of display indicia may be provided on a vehicle instrument panel, and therefore a large number of very closely arranged prisms may be required. By utilizing the configuration disclosed herein, this large number of difficult to install parts may be merged into an integral prism. 
     Further, when the light guide structure  10  of the present embodiment is applied to the illuminated indicating device  1  shown in  FIG. 2 , the number of components that need to be installed may be reduced when compared to a situation where the first light guide  12  and the second light guide  14  are separately provided. In addition, the light guide structure  10  may be reliably installed in the correct position and orientation due to its rigid structure when compared to a situation where the first light guide  12  and the second light guide  14  are separately provided. In this regard, the assembly process for the illuminated indicating device  1  may be improved to be more efficient and less error prone. 
     Further according to the present embodiment, the inwardly V-shaped wall section  164  is configured with the V-angle A 1  which is greater than the V-angle A 2  of the outwardly V-shaped wall section  165 . Due to this, the light trap section  163  of the bridge  16  is inherently configured to block (or reflect back) most or substantially all light from passing therethrough. Therefore, even if the first light guide  12  and the second light guide  14  are integrally formed, the amount of light that leaks between the first light guide  12  and the second light guide  14  may be reduced. As a result, unintended illumination of the indicia  22 ,  24  may be reduced to unnoticeable levels. 
     Further according to the present embodiment, the light blocking function of the bridge  16  is an inherent optical property of the bridge  16  as a result of satisfying the A 1 &gt;A 2  relationship as defined herein, and so there is no need to further process the light guide structure  10  to block light. 
     Further according to the present embodiment, the V-angle A 1  of the inwardly V-shaped wall section  164  is preferably between 110 degrees and 130 degrees, and more preferably between 115 and 125 degrees. In addition, the V-angle A 2  of the outwardly V-shaped wall section  165  is preferably between 80 and 100 degrees, and more preferably between 85 and 95 degrees. Due to this configuration, the light trap section  163  of the bridge  16  may block a significant portion of light from passing therethrough. 
     Further according to the present embodiment, the V-angle A 1  of the inwardly V-shaped wall section  164  is preferably 120 degrees. In addition, the V-angle A 2  of the outwardly V-shaped wall section  165  is preferably 90 degrees. Due to this configuration, the light trap section  163  of the bridge  16  may block an even greater portion of light from passing therethrough. 
     Second Embodiment 
     In the first embodiment, the bridge  16  is formed in a substantially symmetrical manner about the vertices V 1 , V 2 . However, the present disclosure is not intended to be limited to a symmetrical bridge  16 , and a variety of shapes are contemplated. For example, a second embodiment of the present disclosure illustrated in  FIGS. 6 and 7  show an asymmetrical bridge  56 . 
     As shown in  FIG. 6 , a light guide structure  50  according to the second embodiment includes a first light guide  12  and a second light guide  14  in a similar manner as the first embodiment. Accordingly, detailed descriptions related to the first light guide  12  and the second light guide  14  are omitted for brevity. In addition, elements other than the light guide structure  50 , such as the light source  30 , may be configured in the same manner as in the first embodiment, and so descriptions thereof are omitted as well for brevity. 
     Further similar to the first embodiment, the bridge  56  includes a first end  561 , a second end  562 , and a light trap section  563 . The light trap section  563  of the bridge  56  is formed by an inwardly V-shaped wall section  564  and an outwardly V-shaped wall section  565  on opposing sides from each other. The inwardly V-shaped wall section  564  is configured with a V-angle A 1  which is greater than a V-angle A 2  of the outwardly V-shaped wall section  565 . 
     However, the bridge  56  of the present embodiment differs from that of the first embodiment by having an asymmetric shape about the vertices V 1 , V 2 . Specifically, in the present embodiment, the inwardly V-shaped wall section  564  includes a pair of inwardly angled surfaces  564   a,    564   b  which are different from each other in length. In addition, the outwardly V-shaped wall section  565  includes a pair of outwardly angled surfaces  565   a,    565   b  which are different from each other in length. In this regard, the first end  561  is offset from the second end  562  in the height direction (the height direction being an arbitrary direction corresponding to the up-down direction in  FIGS. 6 and 7 ). 
     According to the present embodiment as well, the light trap section  563  still sufficiently blocks light while being formed in an asymmetric manner. This exemplary embodiment is intended to illustrate that the light guide structure of the present disclosure is intended to cover a variety of shapes and forms, as long as there is provided a pair of V-shaped surfaces formed to satisfy the A 1 &gt;A 2  relationship as defined herein. Thus, the light guide structure of the present disclosure may be adapted to a wide variety of applications. 
     Other Embodiments 
     The present disclosure is described with reference to the above embodiments, but these embodiments are not intended to be limiting. A variety of modifications which do not depart from the gist of the present disclosure are contemplated. 
     In the above described embodiments, the light guide structure includes two light guides connected by a bridge. However, the present disclosure is not limited to these specific numbers of light guides and bridges. In alternative embodiments, the light guide structure may include three or more light guides, and a corresponding number of bridges may be provided to connect the plurality of light guides to each other. 
     In the above described embodiments, the light trap section of the bridge is bent in a downward direction (the downward direction being an arbitrary direction corresponding to the up-down direction in  FIGS. 3 to 7 ). However, the present disclosure is not intended to be limited to a light trap section which is bent in a specific direction. Rather, the light trap section may be bent in any direction, as long as the pair of V-shaped surfaces are formed to satisfy the A 1 &gt;A 2  relationship. Accordingly, the light trap section may be formed in a variety of manners which allow flexible manufacturing of the overall light guide structure to specific applications. 
     In the above described embodiments, the pair of inwardly angled surfaces are illustrated as being at substantially the same angle as each other with respect to an overall axial direction of the bridge. In alternative embodiments, the pair of inwardly angled surfaces may be formed at different angles as each other while still maintaining the A 1 &gt;A 2  relationship. The same applies to the pair of outwardly angled surfaces. 
     In the above described embodiments, the inner vertex is described as being positioned closer to the outer vertex than the first end and the second end by a margin X in a direction from the inner vertex to the outer vertex. In general, it is desirable for this margin X to be small, in order to minimize the overall size of the bridge and improve the rigidity of the overall light guide structure. Accordingly, in alternative embodiments, this margin X may be zero instead. Further alternatively, the margin X may be a negative value, i.e., the inner vertex may be positioned further from the outer vertex than the first end and the second end, thereby opening a partial direct path for light to travel from the first end to the second end. Even in this case, by providing the light trap section, a substantial portion of light may be prevented from travelling through the bridge. 
     As used throughout the specification and claims, “substantially” and “about” include at least deviations from ideal or nominal values that are within manufacturing, operational and/or inspection tolerances. 
     The use of terms such as “first”, “second”, “third”, or “fourth” is solely for the purpose of identification, and is not intended to limit the order or relationships of applicable elements.