Patent Publication Number: US-2022214599-A1

Title: Glareshield

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. Provisional Patent Application No. 63/134,358, filed Jan, 6, 2021, the contents of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to a glareshield for imaging systems or vision systems for vehicles. 
     BACKGROUND INFORMATION 
     A typical vehicle vision or imaging system uses one or more cameras to capture images through the windshield of a vehicle. The captured images may be displayed or processed depending on the specific application to aid in the operation of the vehicle. In some cases, in addition to light entering directly through the windshield, light reflected from the dashboard and other surfaces in the vehicle may also fall within the field of view (FOV) of the camera and affect the quality of the captured images. A glareshield (or a stray-light shield) may sometimes be used to block reflections of objects within the vehicle from reaching the camera. In some cases, however, light reflecting from the glare shield may impinge on the camera sensor and affect image quality. Accordingly, a glareshield to alleviate these problems and enable the capture of high-quality images to minimize glare is needed. 
     SUMMARY 
     In an embodiment, a glareshield for a camera of a vehicle is disclosed. The glareshield may include a surface configured to face a windshield of the vehicle and a plurality of similarly shaped ribs on the surface. Each rib of the plurality of ribs may include a windshield-facing surface connected to a camera-facing surface to form a vertex angle therebetween. The vertex angle may be between about 40° and about 100°. 
     In another embodiment, a glareshield for a camera of a vehicle is disclosed. The glareshield may include a surface configured to face a windshield of the vehicle, and a plurality of substantially triangular ribs on the surface. The plurality of ribs may be configured such that a specular component of reflected light from the plurality of ribs during all daylight hours impinges on or passes through an area outside of an entrance pupil of the camera, directly or after further reflection from the windshield. 
     In yet another embodiment, a glareshield is disclosed. The glareshield may include a surface configured to face a windshield of a vehicle, and a plurality of similarly shaped ribs on the surface. A spacing between adjacent ribs of the plurality of ribs may be less than or equal to a height of a rib of the plurality of ribs. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, are used to explain the disclosed principles. In these drawings, where appropriate, reference numerals illustrating like structures, components, materials, and/or elements in different figures are labeled similarly. It is understood that various combinations of the structures, components, and/or elements, other than those specifically shown, are contemplated and are within the scope of the present disclosure. For simplicity and clarity of illustration, the figures depict the general structure of the various described embodiments. Details of well-known components or features may be omitted to avoid obscuring other features, since these omitted features are well-known to those of ordinary skill in the art. Further, elements in the figures are not necessarily drawn to scale. The dimensions of some features may be exaggerated relative to other features to improve understanding of the exemplary embodiments. One skilled in the art would appreciate that the features in the figures are not necessarily drawn to scale and, unless indicated otherwise, should not be viewed as representing proportional relationships between different features in a figure. Additionally, even if it is not specifically mentioned, aspects described with reference to one embodiment or figure may also be applicable to, and may be used with, other embodiments or figures. In the drawings: 
         FIG. 1A  illustrates an exemplary vehicle imaging system having a camera; 
         FIG. 1B  illustrates an exemplary image captured by the camera of  FIG. 1A ; 
         FIG. 2A  illustrates a vehicle imaging system having a camera and an exemplary glareshield; 
         FIG. 2B  illustrates an exemplary image captured by the camera of  FIG. 2A ; 
         FIGS. 3A and 3B  illustrate an exemplary embodiment of a glareshield of the current disclosure; 
         FIGS. 4A and 4B  illustrate specular reflection of sunlight from the glareshield of  FIG. 3A  during different times of day; 
         FIG. 5  is a schematic illustration of quasi-specular reflection of sunlight from the glareshield of  FIG. 3A ; 
         FIGS. 6A and 6B  illustrate the quasi-specular reflection of sunlight from the glareshield of  FIG. 3A  during different times of day; 
         FIG. 7  is an illustration of the exemplary glareshield of  FIG. 3A ; and 
         FIGS. 8A .  8 B, and  8 C are illustrations of different exemplary embodiments of the glareshields of the current disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It should be noted that all numeric values disclosed herein (including all disclosed angles, lengths, widths, thicknesses, ranges, etc.) may have a variation of ±10% (unless a different variation is specified) from the disclosed numeric value. For example, a feature disclosed as being “t” units long (wide, thick, etc.) can vary in length from (t−0.1t) to (t+0.1t) units. Further, all relative terms such as “about,” “substantially,” “approximately,” etc. are used to indicate a possible variation of ±10% (unless noted otherwise or another variation is specified). In some cases, the specification also provides context to the relative terms. For example, a structure described as being substantially triangular may have its vertex angles slightly rounded (as opposed to pointed) and/or its sides slightly curved (as opposed to linear) as shown in the referenced figures. 
     Unless defined otherwise, all terms of art, notations and other scientific terms or terminology used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. Some of the components, structures, and/or processes described or referenced herein are well understood and commonly employed using conventional methodology by those skilled in the art. Therefore, these components, structures, and processes will not be described in detail. All patents, applications, published applications and other publications referred to herein are incorporated by reference in their entirety. If a definition or description set forth in this disclosure is contrary to, or otherwise inconsistent with, a definition and/or description in these references, the definition and/or description set forth in this disclosure prevails over those in the references that are incorporated herein by reference. None of the references described or referenced herein is admitted as prior art to the current disclosure. 
     A typical vehicle vision or imaging system includes one or more cameras (e.g., front facing, side facing, rear facing , etc.) installed in the vehicle. These one or more cameras may include a camera installed on the inside of the front windshield of a vehicle (such as, for example, a car, truck, bus, van, etc.). In some embodiments, the one or more cameras may also include one or more cameras installed on a side and/or a rear of the vehicle. Such an imaging system may be used for a variety of functions such as, for example, object detection, lane warning/keeping, autonomous/semi-autonomous navigation, headlight control, etc.  FIG. 1A  illustrates an exemplary camera  10  of a vehicle imaging system attached inside the front windshield  20  of a vehicle in a front-facing manner.  FIG. 1B  is an illustration of an exemplary image  50  captured by camera  10 . As known to people skilled in the art, camera  10  may be attached to the windshield  20  or other vehicle components (e.g., frame, bracket, etc.) to have a clear view of the scene (e.g., road) in front of the windshield  20 . Camera  10  may include any suitable type of camera known in the art and have an analog or a digital image sensor. During operation, rays of light (or light  30 ) may pass through the windshield  20  and enter the camera  10  through its entrance pupil (or pupil  12 ) to impinge on the camera&#39;s image sensor to create an image (still image, video, etc.) of the scene in front of the windshield  20 . 
     As known to people skilled in the art, pupil  12  of camera  10  is the virtual or optical image of its physical aperture, as seen through the front (or the object side) of the camera&#39;s lens system. The size and location of pupil  12  may differ from those of the physical aperture due to the magnification of the lens. If there is no lens or other optical elements in front of the aperture (e.g., as in a pinhole camera), pupil  12  will have a size and location identical to those of the aperture. A lens (and other optical elements) in front of the aperture may increase or decrease the size of pupil  12  as compared to the size of the aperture. Light  30  that impinges on the area of pupil  12  may enter the camera  10  and create image  50 . 
     As illustrated in  FIG. 1A , in addition to light  30  that passes through windshield  20  and impinges on pupil  12  directly, light rays (reflected light  32 ) may also reflect from surfaces within the vehicle (e.g., dashboard  14 ) and impinge on pupil  12 . This reflected light  32  may create glare  52  in the image  50  recorded by the camera  10 . In some cases, as illustrated in  FIG. 1A , light  32  reflected from dashboard  14  may further reflect off the inside surface of windshield  20  and impinge on pupil  12  to create glare  52 . Glare  52  in image  50  may detrimentally affect the visibility of image  50 . For example, glare  52  may hide or make it difficult to discern objects in a vicinity of glare  52 . 
     With reference to  FIGS. 2A and 2B , in some embodiments, a glareshield  40  may be used to block (or reduce the amount of) the reflected light  32  from dashboard  14  (or other surfaces within vehicle) from impinging on the pupil  12  of camera  10 . As illustrated in  FIG. 2A , the glareshield  40  may be positioned to physically block all, or a substantial portion, of the reflected light  32  from the camera  10 . In some embodiments, the glareshield  40  may be a part of or may be attached to (e.g., to the housing of) the camera  10 . It is also contemplated that, in some embodiments, the glareshield  40  may be attached to the windshield  20  or to other components (e.g., bracket, etc.) of the vehicle. Glareshield  40  may have a top surface  44  that faces the windshield  20 . Generally, as illustrated in  FIG. 2A , the top surface  44  of glareshield  40  may be inclined with respect to the windshield  20 . In some cases, light  30  passing through the windshield  20  may impinge on and reflect from the top surface  44  of the glareshield  40 . A portion of the reflected light  42  from the glareshield  40  may impinge on the pupil  12  of camera  10  (directly or after further reflections from the windshield  20 ) and create glare  54  in the image  50  (see  FIG. 2B ). 
     In general, the glareshield  40  may be configured to reduce the reflection of light therefrom. In some embodiments, the glareshield  40 , or the top surface  44  of glareshield  40 , may be made of or covered with a light absorbing material. In some embodiments, the top surface  44  may have a texture configured to reduce the reflection of light. Additionally, or alternatively, in some embodiments, the top surface  44  of the glareshield  40  may include features or structures configured to reflect the incident light  30  away from camera  10  or pupil  12  of camera  10 . For example, with reference to  FIG. 2A , the structures on top surface  44  of glareshield  40  may reflect the incident light  30  such that the reflected light  42  does not impinge on the pupil  12  of camera  10  (directly or after further reflections from the windshield  20 ). In the example shown in  FIG. 2A , the structures on top surface  44  are shaped in a manner to direct reflected incident light  30  (by one or more reflections off the structures) such that the reflected light is reflected outside a region where the pupil of the camera is located. 
       FIGS. 3A and 3B  illustrate an exemplary glareshield  40  with a top surface  44  that includes exemplary structures configured to reflect incident light  30  away from pupil  12  of camera  10 . In the embodiment illustrated in these figures, these structures include a plurality of triangular ribs  60  arranged side-to-side on the top surface  44  to form a surface having a saw-tooth profile. In some embodiments, as illustrated in  FIG. 3B , the ribs  60  may extend over the entire area of the top surface  44  of the glareshield  40 . However, this is not a requirement. In some embodiments, the ribs  60  may extend over only a smaller portion (e.g., a central portion) of the top surface  44 . 
     As illustrated in  FIG. 3A , a ray of light  30  (e.g., sunlight) that enters the vehicle through windshield  20  may impinge on a rib  60  on the top surface  44  of glareshield  40  and get reflected towards the windshield  20 . A portion of the reflected light  42  may pass through the windshield  20  and exit the vehicle. Another portion of the reflected light  42  may be reflected off the back side of the windshield  20  back into the vehicle. This re-reflected light  42  may again reflect off the ribs  60  of the glareshield  40  towards the windshield  20 . It is contemplated that a portion of the reflected light  42  from the windshield  20  or the glareshield  40  may be directed towards the camera  10 . However, in embodiments of the current disclosure, the glareshield  40  and the ribs  60  may be configured such that the portion of the reflected light  42  directed towards the camera  10  does not impinge on the pupil  12  of camera  10 . Therefore, in embodiments of the current disclosure, reflections from within the vehicle do not create a glare  54  in the image  50  produced by camera  10  (see  FIG. 2B ). In other words, the glare shield top surface may be controlled, e.g., via design of the shape, material and other geometrical and optical characteristics of the glare shield top surface and the ribs so as to not create a glare  54  in the image  50  produced by camera  10 . 
       FIG. 3A  illustrates an exemplary case where the sun is high in the sky in front of the vehicle. In this case, the light  30  entering the windshield  20  is reflected by the glareshield  40  such that the reflected light  42  bypasses the camera  10  entirely. Based on various factors (e.g., time of day, direction of travel, season, etc.), light  30  may pass through the windshield  20  at different angles. The plurality of ribs  60  (or other structures) of the glareshield  40  may be configured such that a ray of light  30  passing through the windshield  20  and impinging on the glareshield  40  at any angle may be directed away from the camera pupil  12 . In other words, the reflected light  42  from the glareshield  40  to the windshield  20  may not be at an angle such that the component of light re-reflected from the windshield  20  will be directed into the camera pupil  12 . 
       FIG. 4A  illustrates an exemplary case where the sun is on the horizon in front of the vehicle. In such a case, light  30  that passes through the windshield  20  impinges the glareshield  40  at a relatively low angle, and light  42  is reflected from the glareshield  40  to the windshield  20  such that the component of the light re-reflected from the windshield  20  impinges the camera  10  below the pupil  12 .  FIG. 4B  illustrates an exemplary case where the sun is high in the sky behind the vehicle. In this case, light  30  that passes through the windshield  20  impinges the glareshield  40  at a relatively higher angle, and light  42  may be reflected from the glareshield  40  to the windshield  20  such that the component of the light re-reflected from the windshield  20  impinges the camera  10  above the pupil  12 . Thus, the reflection of sunlight from the glareshield  40  during all daylight hours may be such that the reflected light  42 , directly or after further reflection from the windshield, impinges on or passes through an area outside of the pupil  12  of camera  10 . 
     In the exemplary embodiments discussed above, the light-reflecting surfaces of the plurality ribs  60  are assumed to be specular (or perfectly flat) such that incident light is reflected in a single outgoing direction (in accordance with the law of reflection that states that the incident angle is equal to the reflected angle). However, while the light-reflecting surfaces of the ribs  60  may be generally flat, in some embodiments, these surfaces may not be perfectly flat because the manufacturing processes (e.g., injection molding, etc.) used to fabricate the ribs  60  may introduce localized roughness on these surfaces. As a result, as schematically illustrated in  FIG. 5 , the reflection from the light-reflecting surfaces of the ribs  60  may be quasi-specular where light is reflected over a range of angles near the specular direction. As would be recognized by a person skilled in the art, during quasi-specular reflection, light reflected from the surface at an angle that fits the law of reflection (i.e., the specular component of reflection) will be higher in magnitude (i.e., higher intensity, energy, luminescence, etc.) than the light reflected at other angles. Therefore, in embodiments where the glareshield  40  reflects light in a quasi-specular manner, some portion of the reflected light  42  may impinge the camera within the area of its pupil  12 . However, the glareshield  40  may be configured such that the specular component of the reflected light does not impinge on pupil  12 , and only the non-specular components of the reflected light below a threshold value of magnitude (intensity, etc.) impinges on pupil  12 . The threshold value of magnitude may be any value that does not cause noticeable (or problematic) glare in the image produced by the camera  10 . 
       FIGS. 6A and 6B  illustrate exemplary embodiments where light  30  impinges a quasi-specular glareshield  40  at relatively lower and higher angles, respectively (i.e., during different daylight hours). In these figures,  42 A represents light at the highest magnitude (the specular component of reflection),  42 B represents a non-specular component of reflection at the threshold magnitude, and  42 C represents a non-specular component of reflection having a value of magnitude below the threshold magnitude. As illustrated in these figures, light  42 A reflected in a specular manner is directed well away from the camera pupil  12 , light  42 B at the threshold magnitude impinges the camera just outside the area of the pupil  12 , and light  42 C below the threshold magnitude impinges within the area of the pupil  12 . However, since the threshold magnitude is selected as the value of magnitude that does not create a glare, reflected light that enters the camera  10  does not produce a glare in the image. 
     The threshold value of magnitude may be selected in any manner (experimentally, numerically, analytically, etc.). For example, experiments (numerical computations, or analytical relations, etc.) may indicate that reflected light  42  having a magnitude that is, for example, ⅛ th  (or ¼ th , or ⅕ th , or ⅙ th ) the magnitude of incident light  30  does not result in noticeable glare (or a problematic glare) in the image produced by the camera. In such cases, this value of magnitude may be selected as the threshold magnitude. It should be noted that any measure of magnitude of light may be used to determine the threshold magnitude. 
     As indicated in the figures above, the plurality of ribs  60  may be arranged on the top surface  44  of the glareshield  40  to form a corrugated shape with a saw-tooth cross-sectional profile. With reference to  FIG. 7 , the glareshield  40  may be inclined with respect to the windshield  20 . Although not a requirement, in typical vehicles, the windshield  20  may also be inclined with respect to a horizontal axis. In the embodiment of the ribs  60  illustrated in  FIG. 7 , each rib  60  has a triangular cross-sectional shape with a windshield-facing surface  62 , a camera-facing surface  64 , and a base  66  forming the three sides of the triangle. As illustrated in  FIG. 7 , the windshield-facing surface  62  faces the windshield  20 , the camera-facing surface  64  faces the camera  10 , and the base  66  is coincident with the top surface  44  of the glareshield  40 . 
     To ensure that the specular component of the light reflected from the glareshield  40  does not impinge on the pupil  12  (and if any portion of the reflected light does impinge on the pupil  12 , the magnitude of the impinging portion is below a threshold magnitude) during all times of the day, the windshield-facing and camera-facing surfaces  62 ,  64  of each rib  60  may be inclined with respect to the windshield  20 . With reference to  FIG. 7 , in some embodiments, the windshield-facing surface  62  of each rib  60  makes an angle of θwith the windshield  20  to move the specular component of reflected light away from the camera pupil when the sun is front of the vehicle. In general, angle θ 1  may vary between about 0° and 90°. In some embodiments, angle θ 1  may be greater than 0° and less than 90°. In some embodiments, angle θ 1  may vary between about 10°-70°, between about 20°-50°, or between about 30°-40°. In some embodiments, for example, when top surface  44  of glareshield  40  has a mirror-like surface finish, angle θ 1  may vary between about 5°-15°, or may be about 10°. In some embodiments, for example, when top surface  44  of glareshield  40  has a quasi-specular surface finish, angle θ 1  may vary between about 10°-40°, or between about 20°-30°. When the sun is low on the horizon in front of the vehicle (for example, see  FIGS. 4A and 6A ), a larger value of angle θ 1  will cause light to be reflected from the glareshield  40  to the windshield  20  such that the component of light re-reflected from the windshield  20  to the camera  10  is directed below the pupil  12 . 
     Alternatively, or additionally, in some embodiments, the camera-facing surface  64  of glareshield  40  makes an angle of θ 2  with the windshield  20  to move the specular component of reflected light away from the camera pupil  12  when the sun is behind of the vehicle. In general, angle θ 2  may be less than or equal to about 100°. In some embodiments, angle θ 2  may vary between about 100°-60°, between about 100°-70°, or between about 90°-70°. When the sun is high in the sky behind the vehicle (see  FIGS. 4B and 6B ), a smaller value of angle θ 2 , will cause the light to be reflected from the glareshield  40  to the windshield  20  such that the component of the light re-reflected from the windshield  20  to the camera  10  is directed above the pupil  12 . 
     It should be noted that, in the discussion above (as illustrated in  FIG. 7 ), angles θ 1  and θ 2  are measured counterclockwise from the windshield  20  to the respective surfaces of the rib  60 . It should also be noted that, although windshield  20  is illustrated as a planar object having a linear profile in  FIG. 7  (and other figures), this is only for the sake of simplicity. In some embodiments, windshield  20  may have a curved profile. In such embodiments, angles θand θ 2  are measured with respect to a tangent at the windshield surface. 
     In some embodiments, in addition to or alternative to θand θ 2  having the angles described above, the vertex angle θ 3  between the windshield-facing and camera-facing surfaces  62 ,  64  of each rib  60  may be between about 40° and about 100°. In some embodiments, angle θ 3  may be between about 45°-90°, between about 60°-90°, or between about 70°-90°. 
     In the figures above (e.g.,  FIG. 7 ), for ease of illustration, each rib  60  of glareshield  40  is illustrated as being perfectly triangular (i.e., with sharp corners and straight sides) with adjacent ribs contacting each other at their base. However, this is not a requirement. In general, as illustrated in  FIGS. 8A-8C , the peaks  60 A and valleys  60 B of the triangular ribs  60  may be rounded (see  FIG. 8A ) or flat (see  FIGS. 8B and 8C ) and adjacent ribs  60  may not contact each other (see  FIGS. 8B and 8C ). That is, in general, each rib  60  may only be substantially triangular, and the plurality of ribs  60  may only have a cross-sectional profile that is substantially sawtooth shaped. As illustrated in  FIG. 8B , the width of each (rounded or flat) peak W p  and/or the width of each (rounded or flat) valley W v  may be smaller than the width W of the rib  60 . With reference to  FIG. 8B , width W v  is the spacing between adjacent ribs  60 . Therefore, in general, the spacing between adjacent ribs  60  (W v ) is smaller than the width W of the ribs  60 . In some embodiments, the widths W p  and/or W v  may be less than or equal to about 10% of W (i.e., W p  and/or W v ≤0.1 W). In some embodiments, the total width of all the peaks  60 A and valleys  60 B of the glareshield  40  (i.e., Σ(W p +W v )) may be less or equal to about 15% (or less or equal to about 10%) of the total width of all the ribs  60  (i.e., EW) in the glareshield  40 . It is also contemplated that, in some embodiments, W v  may be larger than the above listed values (e.g., W v  may be greater than or equal to about W) with W p ≤about 0.1 W. 
     The size of the glareshield  40  and the ribs  60  may depend on the application. In some embodiments, the height H of each rib  60  may be between about 0.5-5 mm, and the width W of each rib  60  may be between about 0.5-5 mm. In some embodiments, the pitch P of the ribs  60  (i.e., the spacing between adjacent ribs  60 ) may be between about  1 - 5  mm. In some embodiments, the width of each peak W p  and/or each valley W v  of the ribs  60  may be less than or equal to the height H of a rib  60 , or less than or equal to about 15% (or ≤about 10%) of the height H of a rib  60  (i.e., W p  and/or W v ≤0.15 H or ≤0.10 H). With reference to  FIG. 8C , in some embodiments, the total width of all the peaks  60 A and valleys  60 B of the glareshield  40  (i.e., Σ(W p +W v )) may be less or equal to about 15% (or ≤about 10%) of the area A of the ribs  60  projected on the windshield  20 . 
     Glareshield  40  may be fabricated from any suitable material (such as, for example, a polymeric or plastic material) using any suitable process (such as, for example, injection molding). In some embodiments, a dark colored or a black colored plastic material may be used to form glareshield  40 . In some embodiments, the glareshield may be formed using a dark colored (or black) non-reflecting or light absorbing material. 
     The above-described embodiments of the glareshield are only exemplary. Many variations are possible. For example, although each rib of the disclosed exemplary glareshields is illustrated as being similarly shaped, this is only exemplary. It is contemplated that, in some embodiments, the glareshield may include ribs of different shapes. It should also be noted that, although some features of the current disclosure are described with reference to a front-facing camera of a vehicle, this is only exemplary. As would be recognized by a person skilled in the art, some or all of the disclosed features may alternatively or additionally be incorporated in cameras that face in other directions (e.g., rear-facing, side-facing, etc.) Other embodiments of the glareshield will be apparent to those skilled in the art from consideration of glareshields disclosed herein.