Abstract:
A virtual image instrument panel display (20) has a display source (22) and reflective elements (24, 26). The display source (22) generates a beam (28) including an image to be viewed. The reflecting elements (24, 26) receive the beam and provide a virtual image of the image of the beam. The virtual image is focused on a viewing plane at a predetermined and substantial virtual distance away from the user to enable easy eye focus transition between the virtual image and distant objects. The folded nature of the optical system provides for a compact package suitable for installation in an automotive dashboard.

Description:
This is a continuation application Ser. No. 07/971,799, filed Nov. 5, 1992, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to instrument panels and, more particularly, to a virtual image instrument panel display having a wide field of view. 
     2. Discussion 
     When driving an automotive vehicle, the driver is constantly viewing the roadway ahead as well as the vehicle dashboard. Generally the dashboard includes gauges such as the speedometer, fuel, water and oil. The driver periodically reviews these gauges to insure that the vehicle is properly functioning. 
     While driving, the driver is constantly focusing and refocusing between the instrument panel, viewed at a close distance, and oncoming traffic, viewed at a long distance. This focusing and refocusing places strain on the eyes of the driver. Heretofore, the driver has had no choice to view the gauges at a distance substantially away from him since the gauges are within the passenger compartment. 
     This substantial distance, a few meters, provides an easier eye focus transition between oncoming traffic and the gauges. Thus, it is desirable to have a panel display which provides a virtual image at a predetermined virtual distance away from the driver so that the driver has an easier eye focus/refocus transition between the oncoming roadway and the instrument panel gauges. 
     SUMMARY OF THE INVENTION 
     According to the teachings of the present invention, an instrument panel display is provided which forms a virtual image at a predetermined virtual distance away from the viewer. The virtual image at the predetermined virtual distance enables easy eye focus transition between the instrument panel and the oncoming roadway. The invention provides a simple compact virtual image display ideal for an automotive instrument panel. The display is configured such that it would be positioned within the vehicle dashboard. The present invention enables adjustment of the display system to accommodate viewing by various drivers. Also, the display would enable the driver to quickly look back and forth from the instrument panel to the oncoming road without strainful eye adjustment. Also, the invention provides a wide field of view as well as a large viewing area with excellent image quality across the field of view. 
     In the preferred embodiment, the virtual image instrument panel display is comprised of the following. A display source generates a beam including an image to be viewed. The beam is directed towards a first mirror. The first mirror receives the beam and reflects it towards a second mirror. The two mirrors form a virtual image of the beam image to be viewed. The ray trace of the beam as it moves from the display source to the first mirror, second mirror and the driver is the shape of the numeral 4 on its side. By this description, it is meant that the optical path from the second mirror to the viewer is folded back through the optical path between the image source and the first mirror and further that these two intersecting optical paths cross at nearly right angles. The virtual image is provided at a viewing plane, for viewing by the driver, at a predetermined virtual distance which enables the driver to quickly look back and forth from the oncoming roadway to the instrument panel without significant eye adjustment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various advantages of the present invention will become apparent to those skilled in the art after a study of the following specification and by reference to the drawings in which: 
     FIG. 1 is a schematic diagram of a vertical ray trace section of a display in accordance with the present invention; 
     FIG. 2 is a schematic view of a vehicle including a virtual image instrument display panel in accordance with the present invention; 
     FIG. 3 is a partial schematic diagram of a vertical ray trace section of a display in accordance with the present invention; and 
     FIG. 4 is a partial schematic diagram, of a horizontal ray trace section of the display in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning to the figures, particularly FIG. 2, a vehicle 10 is illustrated. The vehicle 10 includes a dashboard 12 with a compartment 14 that houses a vertical image instrument panel display illustrated in FIGS. 1, 3 and 4. The virtual image instrument panel display 20 generally includes a display source 22, a first mirror 24 and a second mirror 26. The display source 22 generates a light beam 28 which is directed towards the first mirror 24. 
     The display source 22 may provide all instrumentation needs in the vehicle. The display source 22 may provide the viewer with information regarding the speed of the vehicle, the water temperature, oil pressure, fuel reading or the like, or whatever information the driver may need. The driver would select the desired information to be displayed and this information would be generated by an image source, such as a CRT or a liquid crystal matrix, and then reflected through the system to be viewed by the driver. The driver would be able to view the gauges, dials, maps and/or thermal imagery from the vision enhancement system. Thus, the display 20 would become an integral part of a vision enhancement system equipment package. 
     The first mirror 24 receives the beam 28 from the display source 22 and reflects the beam towards the second mirror 26. The first mirror 24 may be an aspheric mirror, or it could be a powered mirror having an aspheric or higher order surface shape. 
     The second mirror 26 receives the beam from the first mirror 24 and reflects the beam towards the driver. The second mirror 26 is generally a positive power imaging mirror having an aspheric or higher order surface shape. 
     The first and second mirrors 24 and 26 act together to provide a virtual image of the generated beam. Both of the mirrors are generally non-rotationally symmetric aspheric mirrors whose surface shapes are described by Zernike polynomial expressions. 
     The mirrors form a large field of view having about a 10° field of view dimension in the vertical plane and about a 24° field of view in the horizontal plane. In turn, the field of view provides a 3 inch in vertical by 5 inches in horizontal plane for the viewing eye box area 32. 
     The mirrors 24 and 26 provide a virtual image on a viewing plane 30 located at a predetermined virtual distance away from the driver. Generally, the virtual distance may be from several feet to infinity. Preferably, the virtual image is formed at a virtual distance of at least 80 inches in front of the driver. 
     It should be noted that the beam trace from the source 22 to the first mirror 24 to the second mirror 26 and to the viewer 34 traces the shape of the numeral 4 on its side. By this description, it is meant that the optical path from the second mirror 26 to the viewer 34 is folded back through the optical path between the display source 22 and the first mirror 24 and further, that these two intersecting optical paths cross at nearly right angles. This provides the display with its compactness which enables the display to be fit within the dashboard of the vehicle. Generally, the entire package is about 7 inches high by 12 inches wide and 6 inches deep. Also, as seen in FIG. 2, a pivotal adjustment member 36 enables the entire display 20 to be pivoted about a horizontal axis to enable the display 20 to be moved to accommodate various heights of drivers to bring the exit pupil or eye box area to the driver&#39;s eye level. 
     The display 20 provides excellent image quality. Generally, the performance measures of such a biocular system, disparity and accuracy errors, are below the 1.0 milliradian level. 
     A specific prescription for the system in accordance with the present invention is as follows: 
     As is the custom in optical ray tracing, the prescription describes the optical system in an arrangement or order that progresses from the longer conjugate, at the virtual image, to the shorter conjugate, at the display source. This order or arrangement of ray tracing is exactly the opposite of the path actually followed by light from the source to the user&#39;s eye. Such inverse ray tracing is fully supported by the principle of reversibility of light. 
     
         ______________________________________De-                           Thick-     Sizescrip- Radius           Tilt   ness  Ma-  Inchestion  Inches  Aspheric Degrees                         Inches                               terial                                    (v × h)______________________________________Virtual ∞ --       --     60.00 Air  14.0 × 32.8ImageEye   ∞ --       --     -28.00                               Air  3.0 × 5.0BoxSecond 23.6218 see      -22.50 4.00  Refl  5.4 × 11.8Mirror        Note AFirst ∞ see      -25.00 -5.450                               Refl  4.2 × 10.4Mirror        Note BDisplay ∞ --       -9.3436                         --    --   2.85 × 5.27Source______________________________________ 
    
     
         ______________________________________Note A                 Note B______________________________________Z5 = -0.2615 × 10.sup.-2              Z5 = -0.1306 × 10.sup.-1Z8 = -0.1099 × 10.sup.-2              Z8 = -0.3001 × 10.sup.-2Z10 = 0.8978 × 10.sup.-4              Z10 = -0.9867 × 10.sup.-4Z11 = 0.4021 × 10.sup.-4              Z11 = -0.1172 × 10.sup.-3Z12 = -0.3311 × 10.sup.4              Z12 = 0.1156 × 10.sup.-3Z14 = 0.6934 × 10.sup.-5              Z14 = 0.9444 × 10.sup.-5Z17 = -0.4275 × 10.sup.-5              Z17 = 0.8885 × 10.sup.-5Z19 = 0.7370 × 10.sup.-6              Z19 = -0.1117 × 10.sup.-5Z21 = -0.1009 × 10.sup.-6              Z21 = 0.3001 × 10.sup.-7Z22 = -0.8030 × 10.sup.-6              Z22 = 0.1737 × 10.sup.-5Z23 = 0.2497 × 10.sup.-7              Z23 = -0.4879 × 10.sup.-7Z24 = -0.2482 × 10.sup.-9              Z24 = 0.4165 × 10.sup.-9______________________________________ 
    
      (+) thicknesses are to the right; (+) radii have centers to the right; (+) decenters are up; (+) tilts are counterclockwise; decenters done before tilts! surface figure departures according to the equation: ##EQU1## where: Z=surface SAG 
     c=1/RD 
     K=CC=Conic Constant=-(Eccentricity) 2   
     s 2  =x 2  +y 2   
     Sag of a surface designated as &#34;Zern&#34; surface is computed according to the following Zernike equation: ##EQU2## where &#34;Z prev  &#34; is the sag function before this special surface definition. 
     s 2  =x 2  +y 2  and 
     
         ______________________________________Z.sub.1 (x,y) =  1 =        1             ConstantZ.sub.2 (x,y) =  s cos theta =             x             x - tiltZ.sub.3 (x,y) =  s sin theta =             y             y - tiltZ.sub.4 (x,y) =  s.sup.2 =  x.sup.2 + y.sup.2                           FocusZ.sub.5 (x,y) =  s.sup.2 cos 2theta =             x.sup.2 - y.sup.2                           O° astigmatism (3.sup.rd)Z.sub.6 (x,y) =  s.sup.2 sin 2theta =             2 x y         45° astigmatism                           (3.sup.rd)Z.sub.7 (x,y) =  s.sup.3 cos theta =             x (x.sup.2 + y.sup.2)                           x - coma (3.sup.rd)Z.sub.8 (x,y) =  s.sup.3 sin theta =             y (x.sup.2 + y.sup.2)                           y - coma (3.sup.rd)Z.sub.9 (x,y) =  s.sup.3 cos 3theta =             x (x.sup.2 + 3y.sup.2)                           x - clover (3.sup.rd)Z.sub.10 (x,y) =  s.sup.3 sin 3theta =             y (3x.sup.2 - y.sup.2)                           y - clover (3.sup.rd)Z.sub.11 (x,y) =  s.sup.4 =  (x.sup.2 + y.sup.2).sup.2                           3.sup.rd sphericalZ.sub.12 (x,y) =  s.sup.4 cos 2theta =             x.sup.4 - y.sup.4                           0° astigmatism (5.sup.th)Z.sub.13 (x,y) =  s.sup.4 sin 2theta =             2 x y (x.sup.2 + y.sup.2)                           45° astigmatism                           (5.sup.th)Z.sub.14 (x,y) =  s.sup.4 cos 4theta =             x.sup.4 - 6 x.sup.2 y.sup.2 + y.sup.4Z.sub.15 (x,y) =  s.sup.4 sin 4theta =             4 x y (x.sup.2 - y.sup.2)Z.sub.16 (x,y) =  s.sup.5 cos theta =             x (x.sup.2 + y.sup.2).sup.2                           x - coma (5.sup.th)Z.sub.17 (x,y) =  s.sup.5 sin theta =             y (x.sup.2 + y.sup.2).sup.2                           y - coma (5.sup.th)Z.sub.18 (x,y) =  s.sup.5 cos 3theta =             x.sup.5 - 2 x.sup.3 y.sup.2 - 3 x y.sup.4                           x - clover (5.sup.th)Z.sub.19 (x,y) =  s.sup.5 sin 3theta =             3 x.sup.4 y + 2 x.sup.2 y.sup.3 - y.sup.5                           y - clover (5.sup.th)Z.sub.20 (x,y) =  s.sup.5 cos 5theta =             x.sup.5 - 10 x.sup.3 y.sup.2 + 5 x y.sup.4Z.sub.21 (x,y) =  s.sup.5 sin 5theta =             5 x.sup.4 y - 10 x.sup.2 y.sup.3 + y.sup.5Z.sub.22 (x,y) =  s.sup.6 =  (x.sup.2 + y.sup.2).sup.3                           5.sup.th sphericalZ.sub.23 (x,y) =  s.sup.8 =  (x.sup.2 + y.sup.2).sup.4                           7.sup.th sphericalZ.sub.24 (x,y) =  s.sup.10 = (x.sup.2 + y.sup.2).sup.5                           9.sup.th spherical______________________________________ 
    
     The present invention with its wide field of view capabilities can serve all instrumentation needs in a vehicle. The invention provides a simple two mirror design which allows full color imagery and which can be produced in large quantities at low cost using replication or molding techniques. Also while providing a wide field of view, the present invention provides a large eye view box with excellent image quality across the field. The present invention provides a compact size display easy to fabricate at relatively low cost with full color operation, excellent image quality and distortion closely matched to a visual enhancement system sensor optics. 
     It should be understood that while this invention has been described in connection with the particular example hereof, that various modifications, alterations and variations of the present embodiment can be made after having the benefit of the study of the specification, drawings and subjoined claims.