Optical: systems and elements – Holographic system or element – Head up display
Patent
1994-10-13
1998-06-02
Dzierzynski, Paul M.
Optical: systems and elements
Holographic system or element
Head up display
359 14, 359 25, 359630, 359637, 359858, 345 7, 348782, G03H 100, G09G 500, H04N 574
Patent
active
057609314
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an image display unit for displaying a virtual image, and more particularly, to an image display apparatus used as in a heads-up display unit.
BACKGROUND ART
A heads-up display unit, which enables driver visually monitor a meters or the like without averting his or her eyes from the road, is known in the art. This device projects an image of the meter onto the windshield, and forms an image externally in front of the windshield through the incidence of an image reflected by the windshield to the eyes of the driver.
However, such a display on the windshield causes distortion of the virtual image because the windshield itself is a curved surface having different curvatures in the longitudinal and transverse directions. Furthermore, the windshield is not always perpendicular to the display light.
In addition, it is necessary to enlarge the display light from the display because of the necessity of achieving a compact display image forming means with a view to downsizing the apparatus.
As an example of solving these problems the Japanese Patent Provisional Publication No. 4-11525 discloses a method which provides a lens for correcting the distortion of the image caused by the curved shape of the windshield, and separately provides a lens that enlarges the display image from the display unit.
With such a construction in which a lens is separately provided, the size of the entire apparatus becomes large, and poses problems of image distortion caused by the frequent passage of the display light through the lens and losses in the tone clarity of the displayed image.
The present invention was developed in view of the circumstances as described above. The object of the present invention is to provide an image display unit which permits enlargement of the image by means of a single member, and which supplies an image with clear color tones free from distortion.
DISCLOSURE OF THE INVENTION
The present invention provides an image display unit having a display image forming means which forms a display image, and a display means which forms the display image after causing a reflection of the display light emitted from the display image forming means. The display image forming means comprises a reflecting means, provided between the display image forming means and the display means. The display means consists of a member having simultaneously a function of enlarging the display light from the display image forming means, an optical path changing function of causing the display light enlarged by this enlarging function to enter the display means, and a correcting function of correcting the distortion of the display image formed by the display means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional constructional view of the heads-up display unit of a first embodiment of the present invention;
FIG. 2 is a schematic view illustrating the optical system upon exposure of a hologram 3;
FIG. 3 is a descriptive view illustrating the off-axis angle .theta. of the off-axial parabolic concave mirror 14;
FIG. 4 is a schematic sectional constructional view of the heads-up display unit of a second embodiment;
FIG. 5 is a descriptive view illustrating the optical system upon exposure of a hologram according to a third embodiment;
FIG. 6a and FIG. 6b are views illustrating the focal lengths in various directions of a cylindrical lens 22;
FIG. 7 is a graph illustrating the amount of image distortion upon visual recognition of the display images in the third embodiment and the second comparative example;
FIG. 8 is a schematic perspective view of the image display unit of the third embodiment;
FIG. 9 is a perspective view of a toroidal concave mirror of the unit shown in FIG. 8;
FIG. 10 is a sectional view of FIG. 9 cut along the line 10--10;
FIG. 11 is a sectional view of FIG. 9 cut along the line 11--11;
FIG. 12 is a partially cutaway perspective view of the display unit in FIG. 8;
FIG. 13 is a perspective view of the angle adjusting mechanism shown in FIG. 8;
FIG
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R.L. Fisher, "Design methods for a holographic head-up display curved combiner", Optical Engineering, Jun. 1989, pp. 616-621.
Hans-Jurgen Dobschal et al, "Beugungsgitter und Hohlspiegel Zugleich", Feinwerktechnik & Messtechnik, Feb. 1992 pp. 25-27.
R.J. Withrington, "Optical Design of a Holographic Visor Helmet Mounted Display", SPIE, Computer-Aided Optical Design, 1978, pp. 161-170.
Ando Hiroshi
Fukatsu Yoshiaki
Higuchi Masahiro
Kawazoe Naoyuki
Kimura Teiyuu
Dzierzynski Paul M.
Nippondenso Co. Ltd.
Schuberg Darren E.
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