Optical: systems and elements – Holographic system or element – Using modulated or plural reference beams
Reexamination Certificate
2000-02-16
2003-09-02
Chang, Audrey (Department: 2872)
Optical: systems and elements
Holographic system or element
Using modulated or plural reference beams
C359S035000, C359S022000, C359S024000
Reexamination Certificate
active
06614565
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to the field of hologram production and display and, more particularly, to a system and method for producing and displaying a one-step, edge-lit hologram.
BACKGROUND OF THE INVENTION
Edge-illuminated or edge-lit holograms are considered to be a subcategory of holographic displays, in general. Typically, conventional edge-lit holograms are recorded onto a holographic recording material mounted on a material supporting substrate. The edge-lit hologram is then reconstructed by an illumination source that introduces an illumination beam through the edge of the substrate. The illumination beam preferably strikes the material supporting substrate at a steep angle relative to a light ray extending perpendicular to the surface of the substrate.
Edge-lit holograms contain interesting display properties. The holographic image can only be reconstructed with an illumination source introduced through the edge of the substrate. The illumination source is preferably disposed within the display. Thus, the display may be self contained which allows the holographic image to be protected from detrimental effects of ambient light sources. Some conventional systems place the illumination source relatively close to the edge-lit hologram. Additionally, some conventional systems integrate the illumination source with the edge-lit hologram in a stand-alone self-contained display. Such a system can eliminate the need for placement and adjustment of external illumination sources.
However, the recording and production of edge-lit holograms can be problematic. A typical hologram production system introduces an object beam carrying a digitally rendered image to coincide with a reference beam. The interference of the two beams forms a hologram on associated holographic recording material. To satisfactorily record the edge-lit hologram, the reference beam should approximate the high angle of incidence of the intended image reconstruction illumination source, taking into consideration optical characteristics of the material supporting substrate through which the eventual illumination source will travel. In general, a reference beam that sufficiently approximates such properties can be referred to as an “edge-lit reference beam.”
One conventional system for producing edge-lit holograms is disclosed in “A Printer for Edge-Lit Holographic Stereograms,” by Sean T. Nolan, which is a thesis submitted to the Department of Electrical Engineering Computer Sciences of Massachusetts Institute of Technology in February 1994. This reference documents a printer geometry that incorporates a reference beam introduced to a series of lenses that produce an anamorphically collimated reference beam with dimensions of approximately 25 millimeters by 0.4 millimeters. In order to condition the reference beam into an edge-lit reference beam, the disclosed device uses a plateholder consisting of a thick polymethylmethacrilate (PMMA) plinth and glass sandwich. The anamorphic or edge-lit reference beam is then introduced to the holographic recording material through the edge of the PMMA plinth.
This conventional production process is disadvantageous because the plinth is generally permanently laminated to the glass plateholder. Thus, the plinth must be approximately the same size as or larger than the hologram being recorded which typically limits the size of the hologram that the system can produce.
Another disadvantage of many conventional systems is introduction of the reference beam into an edge cut perpendicular to the face of the plate. This arrangement links the thickness of the PMMA plinth to the illumination angle of the hologram and further limits the size of the eventual hologram that can be produced.
A further disadvantage is that many conventional systems can not record full parallax edge-lit holograms and can not record full-color holograms.
One step hologram production technology has been used to satisfactorily record a hologram without the traditional step of creating a preliminary hologram. Both computer image holograms and non-computer image holograms may be produced by such one step technology. Also, not all computer image holograms are produced by one step technology. In some one-step systems, computer processed images of objects or computer models of objects allow the respective system to build a hologram from a number of contiguous, small, elemental pieces known as elemental holograms or hogels. To record each hogel on holographic recording material, an object beam is conditioned through the rendered image and interfered with by a reference beam.
SUMMARY OF THE INVENTION
In accordance with teachings of the present invention, a system and method are disclosed for producing and displaying a one-step, edge-lit hologram that provide significant advantages over prior edge-lit hologram production and display systems and methods.
According to one aspect of the present invention, a system for producing an edge-lit hologram comprises an object beam head, a reference beam head and a frame. The object beam head directs an object beam, and the reference beam head directs an edge-lit reference beam to interfere with the object beam. The holographic recording material and the object beam head and the reference beam head may then be translated in accordance with teachings of the present invention to record the hologram. The translation successively exposes multiple portions of the holographic recording material to interference of the object beam and the edge-lit reference beam to record an edge-lit hologram on the holographic recording material.
For one embodiment, the holographic recording material may be moved relative to the object beam head and the reference beam head which remain in a generally fixed position relative to each other. For another embodiment, the object beam head and the reference beam head may be moved in unison with respect to the holographic recording material which remains in a generally fixed position. For a further embodiment, the holographic recording material may be moved relative to the object beam and the edge-lit reference beam which are also moving substantially in unison with each other relative to the holographic recording material. For some embodiments, the reference beam head may comprise an assembly base and a prism coupled to the assembly base, where the prism is operable to receive the reference beam and condition the reference beam into an edge-lit reference beam.
Another aspect of the present invention includes a system for displaying an edge-lit hologram. The system preferably includes a base enclosure and a light source. The base enclosure may be formed to removably receive an edge of a plinth having an edge-lit hologram mounted thereon. The light source is preferably positioned within the base enclosure and provides an illumination beam to reconstruct the edge-lit hologram when the plinth is received by the base enclosure.
A technical advantage of the present invention is that the size of an edge-lit hologram to be produced is not limited to the size of the associated production optics. For example, a reference beam head incorporating teachings of the present invention may be used to record a hologram having dimensions substantially larger than the reference beam head.
Another technical advantage of the present invention is that an edge-lit reference beam does not have to be introduced into a perpendicular edge. Thus, the size of the edge-lit hologram to be recorded is not limited by the thickness of a plate or plinth having such an edge.
An additional technical advantage of the present invention is that either a horizontal parallax only or a full parallax edge-lit hologram can be recorded.
A further technical advantage of the present invention is that full-color edge-lit holograms may be recorded and displayed with substantially reduced color “crosstalk.”
Still another technical advantage of the present invention is that multiple object beams and multiple edge-lit reference beams may be used to substantially inc
Holzbach Mark E.
Klug Michael Anthony
Campbell Stephenson Ascolese LLP
Chang Audrey
Zebra Imaging, Inc.
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