Holographic device
First Claim
1. An optical display system, comprising:
- projecting means for projecting images of information to be viewed by an observer;
combiner means for reflecting the images to the observer, the combiner means being disposed to allow the observer to view a scene through it and including a holographic optical element that is sandwiched between first and second transparent substrates and is positioned such that the second substrate is nearer to the observer, the holographic optical element having a curved shape and a surface fringe spatial frequency of approximately two or fewer line pairs per millimeter over its usable clear aperture for reducing flare from bright objects viewed through the combiner means; and
means for mounting the projecting means and the combiner means in a predetermined spatial relationship so that the images which strike the holographic optical element pass through only one of the first and second substrates.
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Accused Products
Abstract
There is disclosed herein a holographic optical element (HOE) which is particularly useful for head up display (HUD) systems and similar systems wherein the holographic element is used in a transmission mode as well as in a reflection mode. The element introduces little or no flare when bright light sources are viewed in transmission. The reduction in flare is accomplished by constructing the holographic element so that the fringe density (or spatial frequency) is low or zero at the surfaces of the hologram which forms the holographic element, or stated differently, the fringes in the hologram are formed parallel or substantially parallel to the surfaces of the hologram so that no fringes or very few fringes intersect the surfaces of the hologram. This is accomplished through control of the construction geometry to appropriately orientate the fringes, and a suitable fringe density is approximately two or fewer line pairs per millimeter for a typical application. The exposure rays from a point source used in constructing the hologram are, for example, perpendicular or substantially perpendicular to the surfaces of the gelatin or other sensitive material from which the hologram is made, or variations in the angle of incidence of the exposure rays are otherwise minimized.
159 Citations
28 Claims
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1. An optical display system, comprising:
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projecting means for projecting images of information to be viewed by an observer; combiner means for reflecting the images to the observer, the combiner means being disposed to allow the observer to view a scene through it and including a holographic optical element that is sandwiched between first and second transparent substrates and is positioned such that the second substrate is nearer to the observer, the holographic optical element having a curved shape and a surface fringe spatial frequency of approximately two or fewer line pairs per millimeter over its usable clear aperture for reducing flare from bright objects viewed through the combiner means; and means for mounting the projecting means and the combiner means in a predetermined spatial relationship so that the images which strike the holographic optical element pass through only one of the first and second substrates. - View Dependent Claims (2, 3)
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4. A head up display system for aircraft or other vehicle, comprising:
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projecting means for projecting images of information for an individual in an aircraft; combiner means for collimating light rays carrying the images and for only reflecting the images to the individual, the combiner means being disposed to allow the individual to view scenes outside the aircraft through the combiner means and the aircraft windshield, and the combiner means comprising a curved holographic optical element sandwiched between first and second substrates, the holographic optical element having a surface fringe spatial frequency of substantially zero or fewer than two line pairs per millimeter substantially over its usable clear aperture for reducing flare from bright objects viewed through the combiner means; and means for mounting the projecting means and the combiner means in a predetermined spatial relationship within the aircraft.
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5. A method of constructing a hologram, comprising the steps of:
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applying a holographic recording material on a transparent substrate; and exposing the recording material with only first and second coherent wavefronts of light to create interference patterns therein, the first wavefront of light emanating from a light source, passing through the substrate, and striking the recording material at an angle that is substantially perpendicular to its back surface, the back surface comprising an interface between air and the recording material and functioning to develop and reflect the second wavefront of light.
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6. A method of constructing a hologram, comprising:
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applying on the surface of a transparent substrate a holographic recording material of a first index of refraction; purposefully forming an interface of a second index of refraction at the substrate noncontacting surface of the recording material; and exposing the recording material, through the substrate, to only a first wavefront and a second wavefront of light to produce an interference pattern of holographic fringe lines in the recording material by the interaction of the first wavefront and a second wavefront of light, the second wavefront being derived from the first wavefront and reflecting back into the recording material as a consequence of the change of index of refraction at the interface. - View Dependent Claims (7, 8, 9, 10)
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11. A system for constructing a hologram, comprising:
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a transparent substrate having a layer of holographic recording material of a first index of refraction applied on a surface thereof; means to provide an environment of a second index of refraction that forms an interface with the substrate noncontacting surface of the recording material; and means to apply only a first wavefront of light to pass through the substrate and the recording material, thereby to develop only a second wavefront of light that reflects back through the recording material as a consequence of the change of index of refraction at the interface and interferes with the first wavefront to form the hologram. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method for providing an essentially flare-free head up display for an aircraft or other vehicle, comprising:
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providing images of information to be viewed by an observer; positioning within the observer'"'"'s line of sight a cruved holographic optical element through which the observer can view an outside world scene, the holographic optical element having zero or two or fewer pairs of fringes per millimeter intersecting the surfaces thereof; and directing light rays carrying the images for reflection by the holographic optical element toward the observer, thereby to enable the observer to view simultaneously an essentially flare-free outside world scene and the images of information. - View Dependent Claims (19, 20)
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21. A method of providing an essentially flare-free head up display for aircraft or other vehicle, comprising:
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providing images of information to be viewed by an observer; positioning within the observer'"'"'s direct line of sight a curved holographic optical element having surfaces through which the observer can view an outside world scene, the holographic optical element having zero or two or fewer pairs of fringes per millimeter intersecting the surfaces thereof; and directing light rays carrying the images for only reflection by the holographic optical element toward the observer, thereby to allow the observer to view simultaneously an essentially flare-free outside world scene and the images of information. - View Dependent Claims (22, 23, 24)
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25. An optical display system, comprising:
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projecting means for projecting images of information to be viewed by an observer; combiner means positioned for allowing the observer to view a scene and for receiving through an off-axis angle the images projected by the projecting means, the combiner means including a holographic optical element that is operable in the system for only reflecting the images to the observer and defines a curved viewing surface; image correcting means positioned between the projecting means and the combiner means to correct for image aberrations resulting from the projection of the images through the off-axis angle to the combiner means; and flare minimizing means in the holographic optical element comprising a pattern of holographic fringe lines of which zero or two or fewer line pairs per millimeter intersect the surface of the holographic optical element to provide essentially zero aberration correction for the image and a substantially flare-free scene to the observer. - View Dependent Claims (26, 27, 28)
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Specification