Optical: systems and elements – Holographic system or element – For synthetically generating a hologram
Reexamination Certificate
2001-09-28
2004-08-03
Assaf, Fayez (Department: 2872)
Optical: systems and elements
Holographic system or element
For synthetically generating a hologram
C359S001000, C359S022000, C382S232000, C348S040000
Reexamination Certificate
active
06771402
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the field of holography.
2. Background Information
Holograms are typically created by directing laser light toward a three-dimensional physical object. More particularly, light from a visible spectrum laser is split into two beams, a first of which is directed onto a photosensitive medium, and the second of which is directed toward the object. The photosensitive medium is placed near the object, so that light from the second beam that is reflected by the object will strike the medium. The direct light from the first beam and the reflected light from the second beam combine and interfere to produce an interference pattern on the photosensitive medium.
After the exposure process is complete, the photosensitive medium is developed to fix the interference pattern on and/or in the photosensitive medium. The developed medium can then be used to generate a three dimensional image of the object by directing a beam of coherent light onto the medium so that the interference pattern fixed in the medium can alter the beam to generate the image. This beam is preferably a) coherent and b) has a wavelength that is the same or similar to the wavelength of the coherent light used to initially generate the interference pattern. The interference pattern may have lines that are separated only by several wavelengths of the light used to generate the interference pattern.
The resolution and technical limitations of available photosensitive media, can result in a relatively long exposure time to capture the holographic interference pattern. The average exposure necessary to capture a holographic interference pattern with a photosensitive medium can range, for example, from about a second to about a minute. This long exposure time, coupled with the fine resolution of the interference pattern means that the process of capturing a holographic interference pattern with a photosensitive medium is sensitive to vibration. Thus, intricate and massive arrangements are often used to capture a holographic interference pattern with a high degree of quality. For example, the object to be holographed, a laser and beam splitting mechanism, and the photosensitive medium are often placed together on an isolation table such as a granite slab weighing hundreds or thousands of pounds.
In sum, the process of a) generating a holographic interference pattern using a first portion of coherent light that is reflected from an object and a second portion of the coherent light provided as an off-axis beam, and then b) accurately capturing and then fixing the pattern in a photosensitive medium suitable for later generating a holographic image of an object upon exposure to an appropriate light source, is often cumbersome, resource-intensive and expensive.
However, the three dimensional nature of holographic images can be very useful in a variety of contexts. For example, in a scientific, engineering or business presentation a holographic three dimensional model can be advantageously used to quickly and clearly convey information and understanding to an audience.
Accordingly, a need exists for a method and apparatus that can easily, accurately and inexpensively generate and capture holographic interference patterns and generate corresponding holographic images.
SUMMARY OF THE INVENTION
In accordance with exemplary embodiments of the invention, a method and apparatus are provided for accurately and inexpensively generating a holographic interference pattern based on a mathematical description of an object, fixing the interference pattern in a medium, such that a three dimensional holographic image of the object can be generated using the medium. In accordance with an exemplary embodiment of the invention, a method for storing a holographic interference pattern includes the steps of a) computing the holographic interference pattern based on a mathematical description of an object, and b) forming a medium including the interference pattern. The interference pattern modifies incident light so that the modified light includes a holographic image of the object.
For example, the holographic image can be generated by directing at least one beam of light onto a surface of the medium to modify the beam of light with the interference pattern, the modified beam comprising the holographic image. The incident light or at least one beam of light directed onto the surface of the medium can be coherent light. The step of computing can use quantum electrodynamics. In accordance with an exemplary embodiment of the invention, the computed interference pattern can be partitioned and each partition can be represented as a weighted sum of basis interference patterns. A suitable means such as a digital computer or any other appropriate processing device can be provided for computing the interference pattern based on the mathematical description of the object. A suitable means for forming the medium including the interference pattern is provided, and can include a printer having a sufficiently high resolution to print the computed interference pattern onto a suitable medium, for example a transparent medium. A means for generating the image using the medium including the interference pattern is provided, and can include at least one light source, for example a laser device emitting coherent light.
REFERENCES:
patent: 5194971 (1993-03-01), Haines
patent: 5668648 (1997-09-01), Saito et al.
patent: 6366368 (2002-04-01), Horimai
Mark Lucente, “Holographic Bandwidth Compression Using Spatial Subsampling”, Optical Engineering, Jun. 1996, pp. 1-25.
M. Lucente, “Computational Holographic Bandwidth Compression”, IBM Systems Journal, vol. 35, No. 3&4, 1996, pp. 1-17.
Mark Lucente, “Optimization of Hologram Computation For Real-Time Display”, SPIE Proceeding #1667 “Practical Holograph VI”, Feb. 1992, pp. 1-6.
Assaf Fayez
Hewlett--Packard Development Company, L.P.
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