Synthetic panoramagram

Details Synthetic panoramagram Synthetic panoramagram

1999-09-13

2002-04-02

Nguyen, Phu K. (Department: 2772)

Computer graphics processing and selective visual display system

Computer graphics processing

Three-dimension

Reexamination Certificate

active

06366281

ABSTRACT:

FIELD OF THE INVENTION
The invention is an lenticular stereogram and a method for making the same which provides full panoramagram capability from a stereo pair.
BACKGROUND OF THE INVENTION
There is a substantial prior art in the patent and other literature discussing parallax panoramagram or lenticular stereogram technology. It is not our intention to provide a thorough review of the prior art, but rather to provide a background sufficient to orient one skilled in the art enough to fully appreciate the present disclosure.
Image selection, as Ives has stated, must take place at either the surface of the display or the eyes of the viewer. If the former, then an infinite number of views is required if the image is to be viewed from any location in front of the display. If the latter, then only two views are required. In practice, the interdigitated panoramagram, which is the most practical version of the art under discussion, uses only a handful of images, which may or may not provide acceptable image quality. See L. Lipton, “The Future of Autostereoscopic Electronic Displays”, SPIE Conference Proceedings #1669.
Initial panoramagram cameras provided optical or mechanical means, with either a moving slit or lenticular array, to create a continuum of views within each image column, but the precursor of the panoramagram, the interdigitated parallax stereogram, used sliced and alternated left and right images of a stereopair. This array may be viewed either through a raster barrier (which resembles a Ronchi grating) or an overlaid lenticular surface. In the case of the lenticular method, each lenticule covers an interdigitated set of images, or one column. For either the barrier or lenticular method, image selection is provided more or less at the plane of the display, and there is no requirement for individual viewing devices or eyewear. The lenticular screen typically has a surface of corduroy-like semi-cylindrical elements or lenticules, and has for the most part supplanted the raster barrier because it has much greater light transmission, and because stereo viewing zones are much larger than unwanted pseudo viewing zones.
The term “continuum” as used herein is an approximation in fact due to resolution limitations in any imaging medium or lens system, but the term is more descriptive of the methodology of imaging since no after-the-fact combination is required of separately photographed views. The major benefit of this approach, however derived, is that the observer has relatively good freedom of head placement and can see a stereoscopic image over a broad angle of view.
The interdigitated stereogram, on the other hand, requires exact placement of the eyes in a particular location, and if the head of the observer moves ever so slightly, a pseuodoscopic rather than a stereoscopic image will be seen. The parallax panoramagram is an improvement over the interdigitated parallax stereogram in that it allows for more freedom of view location with respect to the display since quite of bit of head movement is possible. The parallax panoramagram, by incorporating a continuum or multiplicity of views, allows for a wider horizontal angle of view of the display. As previously stated, these cameras are able to produce such a continuum by various means. (The vertical angle of view is not at issue since the lenticular screen is refractive only in the horizontal plane, and head movement up and down does not alter the stereoscopic effect.)
The panoramagram requires a time exposure in some embodiments. The temporally derived spatial parallax information which is captured during the exposure is transformed into the required spatial parallax information. As long as a time exposure is required, certain applications and the ability to shoot many types of subjects are limited. Moreover, panoramagram cameras are complex and costly instruments. Thus, inventors sought means to simplify the panoramagram process and preserve its best quality, namely that the image is more easily viewed than the more primitive interdigitated stereogram.
In a clever variation of the two view interdigitated stereogram, inventors created means to interdigitate a multiplicity of views, in some embodiments captured simultaneously with a number of cameras suitably spaced along a horizontal base. Resembling the interdigitated stereogram, the interdigitated panoramagram neatly attempts to combine the best aspects of both techniques. An array of cameras facing the subject is used to simultaneously photograph the subject, and the images are combined optically or with the aid of a computer to produce the necessary columns of information. In some cases, a single camera is preferred for shooting still-life images, and it is slid along a bar for successive exposures.
It should be noted for clarity that the literature of silver-based photographic panoramagraphy uses the term “interdigitate” to describe the laying down of multiple perspective stripes of images within a column. However, computer graphics people often describe this process as “interleaving,” which is an unfortunate term because it is easily confused with the term “interlacing,” which is widely used to describe electronic displays but with an entirely different meaning.
The panoramagram and its variants have over the years been used for many applications, such as portraiture, advertising, product packaging and magazine reproduction. The technology has also been used for mass consumer snapshot applications with cameras using only three or four lenses.
In the past decade or so, products for snapshots have appeared using the interdigitated concept, but using only three or four lenses or views. While better than a interdigitated stereopair stereogram, the result falls far short of a true panoramagram or a decent interdigitated panoramagram with regard to depth effect and viewing angle. Such products have not had a great deal of commercial success in the marketplace.
In addition to the needs of those requiring still images, viewed either as reflective prints or transparencies, there is also the need for autostereoscopic panoramagram technology as applied to motion picture and electronic imaging displays. The art was applied to movies in the former Soviet Union. Here, a raster barrier was used to view interdigitated stereograms, each view projected with its own lens. After about two decades, the process was abandoned because audiences preferred the polarizing method of image selection since sitting with the head held rigidly was uncomfortable for most people.
There have been some recent attempts to apply the art to electronic displays. The flat matrix type display panel would, at first, appear to be a good fit because of its ability to provide exact registration of an image element with respect to the lenticular screen optical elements. As it turns out, the commercially available products have been disappointing because of poor image quality and the constraint on viewer head placement, as mentioned above. One way to solve the later problem is to employ head tracking technology to shift columns to maintain a stereo rather than a pseudo effect. However, this technology is costly and can only work for a single observer at a time.
One of the most important potential applications of the art is for autostereoscopic television, or 3D TV, which may be viewed without eyewear. Laboratory demonstrations have shown that multiple video projectors projecting to the rear of a screen can be viewed from the front through a lenticular array. But even the use of eight or so projectors still results in severe limitations of observer head movement, and obviously requires a large bandwidth if each image requires its own channel.
One key to making such a television display practical might be to use an approach in which only a stereo pair of images is transmitted, and by some means at the TV set itself, create the additional views required for a true panoramagram display and its attendant benefits. A number of research papers, mostly by workers in Japan and Western Europe, have been presented on this

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