Optical: systems and elements – Diffraction – From grating
Patent
1996-08-30
1997-10-07
Henry, Jon W.
Optical: systems and elements
Diffraction
From grating
359567, 359 32, 359 22, 359613, 359232, 359233, 359460, 359894, G02B 2744, G02B 2608, G02B 2602, G02B 518
Patent
active
056754370
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates, generally, to methods and apparatus for making holograms, and more particularly to a technique for sequentially exposing a film substrate to a plurality of two-dimensional images representative of a three-dimensional physical system to thereby produce a hologram of the physical system.
BACKGROUND ART AND TECHNICAL PROBLEMS
A hologram is a three-dimensional record, for example a film record, of a physical system which, when replayed, produces a true three-dimensional image of the system. Holography differs from stereoscopic photography in that the holographic image exhibits full parallax by affording an observer a full range of viewpoints of the image from every angle, both horizontal and vertical, and full perspective; i.e., it affords the viewer a full range of perspectives of the image from every distance from near to far. A holographic representation of an image thus provides significant advantages over a stereoscopic representation of the same image. This is particularly true in medical diagnosis, where the examination and understanding of volumetric data is critical to proper medical treatment.
While the examination of data which fills a three-dimensional space occurs in all branches of art, science, and engineering, perhaps the most familiar examples involve medical imaging where, for example, Computerized Axial Tomography (CT or CAT), Magnetic Resonance (MR), and other scanning modalities are used to obtain a plurality of cross-sectional images of a human body part. Radiologists, physicians, and patients observe these two-dimensional data "slices" to discern what the two-dimensional data implies about the three-dimensional organs and tissue represented by the data. The integration of a large number of two-dimensional data slices places great strain on the human visual system, even for relatively simple volumetric images. As the organ or tissue under investigation becomes more complex, the ability to properly integrate large amounts of two-dimensional data to produce meaningful and understandable three-dimensional mental images may become overwhelming.
In prior art holograms employing a small number of superimposed holographic images on a single film substrate, the existence of a relatively small percentage of spurious exposed and/or developed photosensitive elements (fog) does not appreciably degrade the quality of the resulting hologram. In contrast, holograms made in accordance with the subject invention, discussed below, typically employ up to 100 or more holograms superimposed on a single film substrate; hence, the presence of a small amount of fog on each hologram would have a serious cumulative effect on the quality of the final product.
A method and apparatus for producing holograms is therefore needed which permits a large number, for example up to several hundred or more different holograms to be recorded on a single film substrate, thereby facilitating the true, three-dimensional holographic reproduction of human body parts and other physical systems which are currently viewed in the form of discrete data slices.
SUMMARY OF THE INVENTION
The present invention provides methods and apparatus for making holograms which overcome the limitations of the prior art.
In accordance with one aspect of the present invention, a hologram camera assembly comprises a single laser source and a beam splitter configured to split the laser beam into a reference beam and an object beam and to direct both beams at a film substrate. The assembly further comprises a spatial light modulator configured to sequentially project a plurality of two-dimensional images, for example a plurality of slices of data comprising a CT scan data set, into the object beam and onto the film. In this manner, a three-dimensional holographic record of each two-dimensional slice of the data set is produced on the film.
In accordance with another aspect of the invention, the entire data set, consisting of one to two hundred or more individual two-dimensional slices, is superimposed o
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Hart Stephen J.
Mailand Ken
Henry Jon W.
Voxel
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