Patent Publication Number: US-2021193086-A1

Title: Head up display configuration

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Application No. 62/945,919 filed on Dec. 10, 2019, the disclosure of which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a head up display (HUD) of a motor vehicle. 
     2. Description of the Related Art 
     A head up display emits light that reflects from the front windshield to be seen by the driver. The light appears to come from a virtual image in front of the driver and in front of the windshield. This type of head up display is currently commercially available. 
     Conventional head up displays create the virtual image by first using a display to create an image. Next, the light from the image is reflected from one or more mirrors. Next, the light from the mirrors is directed up to the windshield and is then reflected from the windshield towards the driver. The mirrors are designed and positioned relative to the display so that the light seen by the driver, which is reflected from the windshield, appears to come from a virtual image that is outside of the vehicle. The mirrors and display are typically contained in a package that occupies a volume beneath the top surface of the dashboard. 
     The “instantaneous eyebox” is the area from which the entire virtual image is visible by one eye of an observer. To be precise, for a driver viewing the virtual image projected by an automotive HUD, the instantaneous eyebox is the area in a vertical plane that is perpendicular to the axis of the vehicle from which the entire virtual image projected by the HUD can be seen by one eye. 
       FIG. 1  illustrates a head up display arrangement of the prior art which enables manual adjustment of the height of the HUD eyebox for the height of the driver.  FIG. 1  shows the method currently used to shift the HUD eyebox vertically to accommodate drivers of a range of heights, with an eyebox that has less vertical height than the range in driver heights. A mirror is rotated to move the instantaneous eyebox to be centered on the driver&#39;s eye position. Rotation of the mirror is accomplished by a motor and gear system. However, the motor and gear system takes up space within the HUD package and adds complexity. The mirror may be an aspheric mirror that rotates about an axis based on manual driver input. This enables the eyebox height to be adjusted to match the driver&#39;s height. 
     Windshield head-up displays currently adjust the height of the eyebox by rotating a mirror. Rotation of the mirror requires the addition of a kinematics system and its assembly. This kinematics system assembly increases the cost and adds volume to the package. 
     SUMMARY OF THE INVENTION 
     The invention may provide a means to vertically move the instantaneous eyebox in an automotive windshield head-up display (HUD) and enable a driver to optimize the height of the center of the eyebox for the driver&#39;s height by changing the area that is active on a fixed display. According to this invention, the instantaneous eyebox is moved by moving the active area on a display, without actual physical motion. 
     This invention may enable the effect of a mirror rotation to be obtained without actually rotating a mirror. Elimination of a physical motion, in this case a mirror rotation, is obtained by using a display system to translate an image on a display. The display does not move, but the same effect is obtained as if the display has been moved. In particular, the size of the aspherical mirror needed to implement the HUD is approximately unchanged from a HUD with a rotating mirror. The mirror of the invention does not rotate, but the same effect of moving the eyebox is achieved. 
     The invention comprises, in one form thereof, a head up display arrangement for a motor vehicle. The arrangement includes a picture generation unit emitting a light field including an image. A mirror is positioned to reflect the light field after the light field has been emitted by the picture generation unit. A windshield is positioned to reflect the light field after the light field has been reflected by the mirror such that a human driver sees the image in the light field after the light field has been reflected by the windshield, and such that the driver sees the image as a virtual image that appears to be outside of the windshield when eyes of the driver are in an imaginary eyebox. An electronic processor is communicatively coupled to the picture generation unit and translates the active area on a fixed display, used to display an image that is viewed by the human driver as the virtual image, to thereby change a vertical level of the eyebox. 
     The invention comprises, in another form thereof, a method of operating a head up display in a motor vehicle, including emitting a light field including an image. The light field is reflected with a mirror after the light field has been emitted. The light field is reflected with a windshield after the light field has been reflected by the mirror such that a human driver sees the image in the light field after the light field has been reflected by the windshield, and such that the driver sees the image as a virtual image that appears to be outside of the windshield when eyes of the driver are in an imaginary eyebox. The active area on a fixed display is translated to thereby change a vertical level of the eyebox. 
     The invention comprises, in yet another form thereof, a head up display arrangement for a motor vehicle including a display screen emitting an image. A mirror is positioned to reflect the image after the image has been emitted by the display screen. A windshield is positioned to reflect the image after the image has been reflected by the mirror such that a human driver sees the image after the image has been reflected by the windshield, and such that the driver sees the image as a virtual image that appears to be outside of the windshield when eyes of the driver are in an imaginary eyebox. An electronic processor is communicatively coupled to the display screen and changes which portion of the display screen emits the image to thereby change a vertical level of the eyebox. A manual control device is communicatively coupled to the processor and enables the driver to cause a change in which portion of the display screen emits the image. 
     An advantage of the invention is that, by simply translating the image on a display instead of rotating a mirror, the need for a mirror rotation mechanism is eliminated along with its associated motor, gears, and drive electronics. 
     Another advantage of the invention is that the noise produced by the mirror rotation mechanism is eliminated. 
     Yet another advantage of the invention is that it eliminates possible failure modes associated with the motor and the rotation mechanism. 
     A further advantage of the invention is that it eliminates the need for clearances for mirror motion, and thus reduces the size and mechanical complexity of the HUD package. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic side view of a head up display arrangement of the prior art. 
         FIG. 2  is a schematic side view of one embodiment of a head up display arrangement of the present invention. 
         FIG. 3  is a schematic side view of a head up display illustrating the effect of having a larger mirror. 
         FIG. 4  is a more detailed schematic side view of the head up display arrangement of  FIG. 2 . 
         FIG. 5  is a flow chart of one method of the present invention for operating a head up display in a motor vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments hereinafter disclosed are not intended to be exhaustive or limit the invention to the precise forms disclosed in the following description. Rather the embodiments are chosen and described so that others skilled in the art may utilize its teachings. 
       FIG. 2  illustrates one embodiment of a head up display arrangement  10  of the present invention including a picture generation unit in the form of a display screen  12 , a mirror  14  and a windshield  16 . Display screen  12  may emit a light field including an image within the light field.  FIG. 2  also illustrates how the height of an eyebox  18  may be moved vertically between positions A and B by translating the image on display screen  12  between positions A and B. Mirror  14  is stationary and is in the same position regardless of whether the image on display screen  12  is at position A or position B. An image centered at position A on display screen  12  reflects from mirror  14  to create a virtual image  20  that appears to be at position A from eyebox center location A. Similarly, an image centered at position B on display screen  12  reflects from mirror  14  to create a virtual image  20  that appears to be at position B from eyebox center location B. 
     The driver may be provided with a manual control device  22  to move the image between positions A and B on display screen  12 . As the image moves from position A to position B on display screen  12 , eyebox  18  moves vertically from position A to position B. 
       FIG. 3  illustrates the effect of having a larger mirror in a head up display.  FIG. 3  illustrates a way of increasing the size of the eyebox to accommodate the full range of driver height with a fixed aspherical mirror and a fixed image on the display. The vertical size of the mirror is increased. That is,  FIG. 3  shows the effect of keeping the image on the display screen or picture generation unit (PGU) stationary and increasing the vertical size of the aspherical mirror. The effect is that the size of the eyebox is increased so the instantaneous eyebox covers the entire range of the driver&#39;s height. The size of the HUD eyebox is increased using a stationary aspheric mirror and a fixed image on the PGU. If the aspheric mirror and the image on the PGU are kept stationary, the optical footprint on the mirror grows, making the mirror larger, more costly, and more difficult to package. 
       FIG. 4  illustrates head up display arrangement  10  of  FIG. 2  in greater detail. The image is moved or translated on PGU  12 , but aspherical mirror  14  is kept stationary. The vertical height of aspherical mirror  14  does not increase to cover the entire range of driver height. Instead, the image is moved vertically on the surface or display screen of PGU  12 . The image moves on PGU  12  to eliminate the need to move mirror  14 , while keeping the optical footprint on mirror  14  minimized. The image moves vertically along the PGU surface to center the eyebox on the eye position. The optical footprint on mirror  14  may be unchanged for all eyebox locations. The eyebox is moved to match the driver&#39;s eye location. The vertical size of mirror  14  is the same as for a rotating mirror. 
       FIG. 5  illustrates one method  500  of the present invention for operating a head up display in a motor vehicle. In a first step  502 , a processor means is used to select an area on display screen  12  within which to display an image that will allow a human driver to see a virtual image from within a pre-determined eyebox. 
     In a next step  504 , an image to be displayed as a virtual image is mapped to the pre-determined area on display screen  12 . 
     Next, in step  506 , the image created on display screen  12  produces a light field that reflects from mirror  14 , reflects from windshield  16 , and is seen by a human driver as a virtual image  20  that appears to be outside of windshield  16  when the eyes of the driver are within an imaginary eyebox  18 . 
     In a final step  508 , the image is translated on display screen  12  to thereby change a vertical level of the eyebox. For example, manual control device  22  may enable the driver to move the image between positions A and B on display screen  12 . As the image moves from position A to position B on display screen  12 , eyebox  18  moves vertically from position A to position B. 
     While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.