Liquid crystal cells – elements and systems – Liquid crystal system – Stereoscopic
Reexamination Certificate
1996-07-11
2002-03-19
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Stereoscopic
C349S096000, C349S098000, C359S023000, C348S058000
Reexamination Certificate
active
06359664
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of three dimensional (3-D) stereoscopic imaging and display technologies in general and relates more particularly to stereoscopic photography, television, motion picture, printing and computer displays.
2. Description of Related Art
The binocular vision of humans perceives the real world as 3-D images. This fact results from a combination of the physiological and psychological properties of the human pair of eyes. The pair of eyes is the most important source of depth perception. Because of its spherical shape, the retina of a single eye collects only two-dimensional image information. Therefore, cues of the third dimension (depth) can never be collected by the retina of a single eye.
The inventions of printing (1450) and photography (1839) enabled man to cheaply mass-produce pictures for popular use. There has always been the awareness that these technologies lacked the third dimension (depth), and therefore, the desire to invent ways to faithfully capture and reproduce nature as 3-D images has persisted throughout the ages. Around the year 1600, Giovanni Battista della Porta produced the first artificial 3-D drawing. The history and evolution of 3-D imaging techniques are surveyed in T. Okoshi, Three-Dimensional Imaging Techniques, Academic Press, New York, 1976, and T. Okoshi, Three Dimensional Displays, Proc. IEEE, 68, 548 (1980). Accounts of the most recent activities in 3-D technologies were recently presented in the Conference on Three-Dimensional visualization and Display Technologies, in Los Angeles, Calif., Jan. 18-20, 1989 and published in the Proceedings of the International Society for Optical Engineers, SPIE volume 1083, edited by Woodrow E. Robbins and Scott S. Fisher.
3-D imaging is classified into two major classes: Autostereoscopic Imaging, a technique which produces 3-D images that can be viewed directly without the aid of wearing special eye-glasses; and Binocular Stereoscopic Imaging, a technique that requires wearing special eye-glasses.
Autostereoscopic Imaging
This 3-D class is further broken into four subclasses:
I.1 Parallax Barrier
I.2 Lenticular Sheet
I.3 Holographic
I.4 Multiplanar free viewing
The operating principles of these techniques are reviewed in detail in Three-Dimensional Imaging Techniques. The Parallax Barrier technique is one of the earliest techniques and was experimented with in the first quarter of this century. However, because of its complexity and the dark images it produced, it fell out of favor and was abandoned. The Lenticular Sheet technique is still used today to produce 3-D color postcards. It requires multi-cameras or one camera with multiple lenses. The recording process is quite complex and the final product is obtained after four or more images with different perspectives of the object are aligned and mounted to a sheet of a clear plastic cylindrical micro-lens array. Vertical misalignment results in discomfort and headaches. The technique becomes expensive for large prints, and has significant technical problems. Because of the use micro-lenses, the image does not look the same to different viewers in different viewing positions. Also the depth information in the image can be distorted and can depart significantly from the original object. Finally, this technique cannot be used for TV, computer displays, or computer printers.
The Holographic technique described in Three-Dimensional Imaging Techniques and Three Dimensional Displays, and by L. F. Hodges et al. in Information Displays, 3, 9 (1987), has shown promise for still images but not for TV or movies. It requires very sensitive and expensive film, and is unable to produce large holograms because of sensitivity to vibration. Also, because of the requirement for coherent monochromatic sources for recording and reconstruction (viewing), it is difficult to produce full color holograms. Holography is very expensive and is not used for mass markets as in conventional photography.
The Multiplanar technique described by M.C. King and D. H. Berry, Appl. Opt., May 9, 1980; and R. D. Williams and F. Garcia Jr., SID Digest, 19, 91 (1988), is the only member of the Autostereoscopic class which has a commercial product. It uses a verifocal mirror
1
which is a reflective membrane mounted on a speaker
2
as shown in FIG.
1
. The speaker
2
causes the membrane to vibrate and to vary the focal length of the mirror. When the image of a cathode ray tube (CRT)
3
is viewed through this mirror it appears as a 3-D image
4
. The information of the third dimension (depth) is represented by the different focal lengths which image different z planes of the original object. While this method has been successful in realizing a 3-D system for some special applications, it has serious limitations: i) it is not general purpose, i.e., the method cannot be used for 3-D hard copy production such as photography and printing; ii) it cannot be used for mass viewing as, for example, in a motion picture theatre; iii) it cannot be used for 3-D TV without making the massive investments in existing TV production equipment, broadcast equipment, TV sets, VCR, and other video equipment obsolete; and iv) has poor depth resolution given by the ratio of frame frequency to the mirror vibrating frequency. Other limitations such as cost and bulkiness, will limit the utility of this verifocal method.
Binocular Stereoscopic Imaging
This 3-D class has had the most relative success in narrow fields. To record an image, one generally requires two cameras, as illustrated in
FIG. 2
, one for the left image
5
and the other for the right image
6
. In order to simulate the human stereoscopic vision, the cameras are separated by the pupil distance of 6.5 cm, which is the average distance between the two eyes. There are two techniques for coding the left/right information: Color Coding, as described in Three-Dimensional Imaging Techniques; and by L. Lipton, Foundations of the Stereo Cinema, Van Nostrand Reinhold, New York, 1982; and Polarization Coding, as described in Hartmann and Hikspoors, Information Displays, 3, 15 (1987); L. F. Hodges and D. F. McAllister, Information Displays, 5, 18 (1987); P. Bos et al., SID Digest, 19, 450 (1988).
Color Coding: In this technique, two different color filters
7
,
8
are placed in front of the cameras; for instance, green
8
in front of the left camera
5
and red
7
in front of the right camera. When the images are displayed as in
FIG. 3
, the viewer wears eye glasses
9
having the corresponding color filters, green, for the left eye, and red for the right eye. Thus, the left eye sees only the left image
10
(green image) of the object
15
taken by the left camera, while the right eye sees only the right image
11
(red image) taken by the right camera. This technique has been used for decades to produce movies with 3-D sensation and it can be used for 3-D TV. For real time TV (transmission and reception of live scenes), one requires extra hardware to synchronize TV cameras and to electronically combine the red with the green information before transmission. The TV receiver does not require any modification. This technique has several limitations:
1. It does not provide a full color display;
2. It has been shown to lead quickly to eye fatigue;
3. The image display is dark;
4. The filter eye glasses are dark and cannot be used to view the natural 3-D environment when the viewer turns away from the artificial 3-D scene;
5. Special new TV production equipment and transmission hardware are required; and
6. Vertical misalignment leads to eye discomfort, fatigue, and headaches.
Polarization Coding: Electromagnetic plane waves have electric and magnetic fields which are transverse to the propagation direction, as shown in FIG.
4
. There are two possible orientations for each of the electric and magnetic fields. These orientations are called polarization states. The E
1
and H
1
transverse fields represent one wave having polarization P
1
while the E
2
and H
2
transverse fields repre
Brill Gerow D.
Nguyen Dung
Perkowski PC Thomas
Reveo Inc.
Sikes William L.
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