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Heads-up and heads-down displays employing holographic stereograms
| Details |
Inventors: Molteni, William J.; Volchok, William J.;
Assignee: Polaroid Corporation (Cambridge, MA)
Primary Examiner: Lerner; Martin
Assistant Examiner:
Attorney, Agent or Firm: Vale; John S.
Heads-up and heads-down displays employing holographic stereograms are provided. The stereograms can be oriented perpendicular to the user's line of sight (the "90.degree. case") or at angle to the line of sight (the "non-90.degree. case"). The stereograms are produced using a three-step process in which a series of two-dimensional perspective views are prepared, a H.sub.1 hologram is prepared from the two-dimensional perspective views, and a H.sub.2 hologram is prepared from the H.sub.1 hologram. For the non-90.degree. case, the two-dimensional perspective views are oriented at an angle relative to the plane of the H.sub.1 hologram during the preparation of that hologram. Similarly, during the preparation of the H.sub.2 hologram for this case, the H.sub.2 hologram is oriented at an angle relative to the H.sub.1 hologram. In this way, the viewing slits generated by the holographic stereogram are located in the vicinity of the user's eyes for the non-90.degree. case as is desired. In certain embodiments, the two-dimensional perspective views are transformed prior to being recorded on the H.sub.1 hologram. |
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DETAILED DESCRIPTION In view of the foregoing state of the art, it is an object of the present invention to provide improved heads-up and heads-down displays.
More particularly, it is an object of the present invention to provide improved heads-up and heads-down displays employing holograms which contain image information, i.
e.
, to provide improved IHDs.
It is a specific object of the invention to provide improved IHDs which can be used with broadband light sources and not suffer from significant color blur.
It is a further object of the invention to provide IHDs which do not suffer from significant color blur but yet can be readily and inexpensively manufactured.
It is an additional object of the invention to provide IHDs which can be used with relatively weak light sources, such as, low powered incandescent lamps.
It is a further object of the invention to provide IHDs of the foregoing types wherein the user perceives that the image produced by the IHD lies in a plane rotated relative to that of the hologram used in the IHD and/or is translated relative to the center of the hologram, including being made to appear in front of or behind the plane of the hologram.
To achieve the foregoing and other objects, the invention in accordance with certain of its aspects provides an optical system for displaying first and second images to a user comprising: (a) a viewing window for viewing the first image, said first image being non-holographic and said viewing window presenting a field of view of the first image to the user; (b) a substantially transparent holographic stereogram for forming the second image, said stereogram and said second image being in said field of view; and (c) a source of illumination for illuminating the stereogram to form the second image.
In certain preferred embodiments of the invention, the second image formed by the holographic stereogram is formed close to the hologram, i.
e.
, within the physical volume occupied by the hologram or close to that volume.
In this way, the color blur problem associated with a multi-wavelength light source is addressed since the formation of the image close to the hologram means that the multiple wavelengths do not have a chance to disperse before the image is formed
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Optical Systems 
