Patent Publication Number: US-2017371165-A1

Title: Head up display with stabilized vertical alignment

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Application No. 62/353,528 filed on Jun. 22, 2016, which the disclosure of which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The disclosure relates to a head up display (HUD) in a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     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. 
     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 reflected from the windshield. 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. 
     SUMMARY 
     The present invention may provide a head up display wherein the perceived vertical alignment of the displayed graphics is kept constant, independent of adjustment of the HUD eye box position for the height of the driver. The adjustment of the HUD for vertical height may involve changing the rotational angle of a mirror. Either the angle of the mirror can be measured, or software can keep track of the current position of the mirror. In some HUDs, the mirror is placed in a “park” position each time the vehicle is turned off. Alternatively, instead of actually measuring the rotational angle of the mirror, the commanded angle can be determined. Given the current position (or commanded position) of the mirror, the software that places the graphical images on the display internal to the HUD can compensate for any dependence of perceived vertical height of graphics on the vertical position of the eye box. 
     In one embodiment, the invention comprises a head up display arrangement for a motor vehicle, including an image source emitting a light field based on image data. A mirror is positioned to reflect the light field such that the light field further reflects off of a windshield of the motor vehicle and is visible to a driver of the vehicle as a virtual image while eyes of the driver are disposed within an eyebox. A driver&#39;s input device is coupled to the mirror and changes an angle of reflection of the mirror and thereby changes a vertical level of the eyebox in response to input from the driver. A controller is communicatively coupled to the image source and produces the image data. The controller determines the angle of reflection of the mirror, and adjusts the image data in response to the change in the angle of reflection of the mirror such that a vertical level of the virtual image is unchanged by the change in the angle of reflection of the mirror. 
     In another embodiment, the invention comprises a head up display method for a motor vehicle, including emitting a light field based on image data. The light field is reflected with a mirror such that the light field further reflects off of a windshield of the motor vehicle and is visible to a driver of the vehicle as a virtual image while eyes of the driver are disposed within an eyebox. An angle of reflection of the mirror is changed, thereby changing a vertical level of the eyebox, in response to input from the driver. The angle of reflection of the mirror is determined. The image data is adjusted in response to the change in the angle of reflection of the mirror such that a vertical level of the virtual image is unchanged by the change in the angle of reflection of the mirror. 
     In yet another embodiment, the invention comprises a head up display method for a motor vehicle, including emitting a light field based on image data. The light field is reflected off of a windshield of the motor vehicle such that the light field is visible to a driver of the vehicle as a virtual image while eyes of the driver are disposed within an eyebox. A trajectory of the light field is changed to thereby change a vertical level of the eyebox, in response to input from the driver. The image data is changed in response to the change in the trajectory of the light field such that a vertical level of the virtual image is unchanged by the change in the trajectory of the light field. 
     An advantage of the present invention is that it may correct the vertical position of the HUD virtual image after the vertical position of the eyebox has been adjusted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings. 
         FIG. 1  is a schematic diagram of one example embodiment of a HUD arrangement of the present invention. 
         FIG. 2  is a schematic diagram of an example of adjustment of the virtual image in response to a change in the vertical level of the eyebox. 
         FIG. 3  is a flow chart of one example embodiment of a head up display method of the present invention for a motor vehicle. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates one embodiment of a HUD arrangement  10  of the present invention, including a driver&#39;s input device  12 , a HUD controller  14 , HUD hardware  16 , and a windshield  18 . HUD hardware  16  may include a light emitter  19  and at least one mirror  21 . Input device  12  may be coupled to mirror  21  such that input device  12  may change the orientation of mirror  21 . During use, light emitter  19  of hardware  16  emits a light field  20  that is reflected by mirror  21 , and that is further reflected by windshield  18  toward a driver  22 . The light field is visible to driver  22  as a virtual image  24  outside of windshield  18 . The trajectory of light field  20  defines the location of an eyebox  26 , which is the set of boundaries of the area in which the driver&#39;s eyes must be for virtual image  24  to be visible. 
     In order to move the vertical position of eyebox  26  into alignment with the vertical position of the driver&#39;s eyes, which may depend upon his stature, the driver may adjust input device  12 . However, the vertical movement of eyebox  26  may also change the vertical position of virtual image  24 , which may not be desirable if virtual image  24  then obscures the driver&#39;s view of the road in front of him, or draws his attention away from the road. That is, adjustment of the head up display for the height of the driver (e.g., by rotating a mirror) may undesirably change the perceived vertical height of graphics relative to the vehicle in front. 
     According to the invention, arrangement  10  may compensate for the commanded vertical position of graphics displayed on virtual image  24 , and for the perceived change in the vertical position of virtual image  24 , caused by the vertical adjustment of eye box  26  to compensate for driver height. The vertical adjustment of eye box  26  may be achieved by rotating a mirror  21  within hardware  16 . In order to determine the rotational position of the mirror after the driver&#39;s adjustment, the rotational position of a shaft  28  that carries the mirror may be determined by a shaft position sensor  30 . Although shaft  28  is shown in a particular horizontal orientation in  FIG. 1  for ease of illustration, it is to be understood that shaft  28  may be at any orientation relative to the other components of  FIG. 1 . In one embodiment, shaft  28  is oriented in alignment with a horizontal direction into the page of  FIG. 1 , and extends in lateral directions to the right and left of the vehicle and driver  22 . 
     There are several possible ways to measure the angle of the shaft relative to a fixed reference, and thus shaft position sensor  30  may be of many different possible types. These include resistive, capacitive, inductive, magnetic, and optical types of shaft position sensors. In principle, any one of these may be used within the scope of the invention to determine the position of the shaft, and hence, the position of the mirror. 
     The mirror adjustment in the HUD to compensate for driver&#39;s height, changes the apparent height of the HUD virtual image above the road. The HUD can determine the setting of the mirror angle that adjusts for the driver&#39;s height. Software may be used to compensate in the image data for any change in the apparent height of the HUD virtual image above the road. 
       FIG. 2  illustrates an example of adjustment of virtual image  24  in response to a change in the vertical level of eyebox  26 . The left half of the drawing shows the position of virtual image  24  and the horizon  28  within eyebox  26 . Virtual image  24  is shown as a circle for clarity of illustration, but may more typically be one or more alphanumeric characters. The right half of the drawing shows eyebox  26  after the driver has adjusted its vertical position, and virtual image  24  after software within HUD controller  14  has adjusted the position of virtual image  24  within eyebox  26  to compensate for the vertical adjustment of eyebox  26 . As can be seen from a comparison of the left and right sides of  FIG. 2 , the vertical level of virtual image  24  relative to horizon  28  is unchanged despite the position of eyebox  26  being changed with respect to horizon  28 . 
       FIG. 3  illustrates one example embodiment of a head up display method  300  of the present invention for a motor vehicle. In a first step  302 , a light field is emitted based on image data. For example, light emitter  19  of hardware  16  may emit a light field  20  based upon image data received from HUD controller  14 . 
     Next, in step  304 , the light field is reflected by a mirror such that the light field further reflects off of a windshield of the motor vehicle and is visible to a driver of the vehicle as a virtual image while eyes of the driver are disposed within an eyebox. For example, light field  20  may be reflected by mirror  21  such that light field  20  further reflects off of windshield  18  of the motor vehicle and is visible to driver  22  of the vehicle as a virtual image  24  while eyes of driver  22  are disposed within an eyebox  26 . 
     In a next step  306 , an angle of reflection of the mirror is changed, thereby changing a vertical level of the eyebox, in response to input from the driver. For example, driver  22  may use input device  12  to change an orientation of mirror  21 , thereby changing the trajectory of light field  20 , and thereby changing a vertical level of eyebox  26 , as shown in  FIG. 2 . 
     In step  308 , the angle of reflection of the mirror is determined. For example, the rotational position of the shaft that carries mirror  21  may be determined by resistive, capacitive, inductive, magnetic, and/or optical methods. 
     In a final step  310 , the image data is adjusted in response to the change in the angle of reflection of the mirror such that a vertical level of the virtual image is unchanged by the change in the angle of reflection of the mirror. For example, as shown in  FIG. 2 , the image data from HUD controller  14  may be changed in response to the determined angle of reflection of the mirror such that a vertical level of virtual image  24  is unchanged by the rotation of mirror  21 . By adjusting the image data, the contents of virtual image  24 , such as the circle shown in  FIG. 2 , may be moved within eyebox  26  such that the vertical level of the contents of virtual image  24  are unchanged even though the vertical level of eyebox  26  has changed. 
     The foregoing description may refer to “motor vehicle”, “automobile”, “automotive”, or similar expressions. It is to be understood that these terms are not intended to limit the invention to any particular type of transportation vehicle. Rather, the invention may be applied to any type of transportation vehicle whether traveling by air, water, or ground, such as airplanes, boats, etc. 
     The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications can be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention.