Apparatus for three-dimensional viewing

A system for presenting stereoscopic images to a viewer includes a screen for presenting first and second images and a plurality of louvers for isolating the images for viewers located back from the screen along predetermined sight lines. In a first embodiment, a pair of stereoscopic images are presented simultaneously on co-planar screens, and fixed isolation louvers isolate the images for a viewer positioned along a center line from the viewing enclosure. In a second embodiment, the stereoscopic images are presented sequentially on a common screen, and movable louvers are provided for isolating the images first from the right eye and then from the left eye. In both cases, viewers may experience three-dimensional images without having to wear glasses or goggles and without having to come up immediately to the viewing device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to devices for presenting 
three-dimensional images to viewers. More particularly, the invention 
relates to a device having fixed or movable louvers capable of isolating 
right and left stereoscopic images for one or more viewers located within 
a generally fixed area spaced-away from the viewing device. 
Three-dimensional or stereoscopic viewing relies on the presentation to the 
viewer of a pair of images of the same scene or object, where the images 
differ only in parallax corresponding to the distance between the viewer's 
eyes. Usually, the images are taken by a stereoscopic camera having a pair 
of lenses spaced-apart by a distance approximately equal to that between a 
pair of eyes. A number of devices have been developed for viewing such 
pairs of images in order to enhance the apparent three-dimensionality. 
Perhaps the best known of such devices are hand-held stereoscopic viewers 
(stereoscopes), such as the Viewmaster.RTM., where right and left images 
are totally isolated by a barrier, lens viewing mechanism, or both. Such 
devices, of course, are only suitable for one viewer at a time and are 
generally limited to viewing still images. 
For groups of viewers, systems have been developed for isolating right and 
left images which are simultaneously projected onto a screen. Usually, the 
images are distinguishable, for example by color or polarization, and the 
viewer wears glasses having lenses capable of transmitting only one image 
to each eye. For example, images projected simultaneously in red and green 
may be filtered from each other using green and red filters. 
Alternatively, images polarized by 90.degree. may be simultaneously 
projected and separated by correspondingly oriented polarized lenses. 
While such three-dimensional viewing systems are generally functional, 
many viewers object to having to wear glasses. However, the use of colored 
images for isolation generally limits the ability to project full color 
images, and the isolation provided by polarization of images is not 
complete. 
It has long been an object to be able to present three-dimensional images 
to groups and audiences without the need for the individual viewers to 
wear glasses or other apparatus for isolating images. A number of systems 
have been proposed to such end. For example, simultaneously projected 
polarized images may be isolated by placing a pair of large polarizing 
screens between the audience and the images. The screens may then be 
shifted laterally in order to isolate the images from the right and left 
eyes, respectively. Although functional in theory, as a practical matter 
the polarizing screens are not sufficiently effective in isolating images 
to present a quality three-dimensional image. 
For the above reasons, it would be desirable to provide improved systems 
for presenting three-dimensional images to groups of viewers, where the 
viewers do not need to wear image isolating devices, such as filter 
glasses. 
2. Description of the Background Art 
Stereoscopic imaging devices are described in U.S. Pat. Nos. 2,639,653; 
2,974,562; 3,334,179; 3,439,972; 3,495,891; and 4,469,415; and in Japanese 
patent No. 60-37520. U.S. Pat. No. 2,974,562 describes a viewer which 
isolates polarized right and left images using a pair of transparent 
polarizing panels. By shifting the panels back and forth, view of a common 
screen can be alternately blocked for the left and right eyes. A similar 
concept is disclosed in U.S. Pat. No. 3,439,972, where two images are 
divided into a plurality of parallel vertical strips, and a vertical 
grating is used to isolate alternate strips from the right and left eyes 
respectively. 
SUMMARY OF THE INVENTION 
The present invention provides a system for displaying a stereoscopic image 
without the need for viewers to individually use filters, lenses, glasses, 
or other devices for isolating right and left images. The system is 
suitable for single viewers, or may be adapted for groups of viewers, and 
may be used to present either still images, or, more usually moving 
images. 
The system comprises a screen for presenting right and left images which 
together define the stereoscopic image. The right and left images may be 
presented simultaneously at adjacent locations on the screen, or may be 
presented sequentially at the same location on the screen. In the first 
case, fixed louvers are positioned so that the right and left eyes of 
viewers within a predefined area are generally limited to the right and 
left images, respectively. In the other case, movable louvers are placed 
so that, in a first position, only the right eye can see the image on the 
screen and, in a second position, only the left eye can see the image on 
the screen. By synchronizing motion of the louvers and presentation of 
right and left images, a stereoscopic presentation can be maintained. For 
best results, the viewers should be located generally along a central line 
perpendicular to the plane of the screen. The degree of lateral divergence 
from the center line will depend on the precise geometry and size of the 
screen and louvers. 
The images may be presented in any convenient fashion, typically being 
projected on a screen, either by film projection or by electron video 
projection. In the case of systems where separate right and left images 
are projected simultaneously, two separate screens will be utilized for 
projection. In the case where right and left images are projected 
sequentially on a single screen, the film can be arranged to project 
alternate series of each of the desired two images. Similarly, electronic 
video projection can be arranged to project the two images in the desired 
alternating sequence.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
Referring to FIG. 1, a system for simultaneously viewing a pair of 
stereoscopic images comprises an enclosure 10, a pair of image screens 12 
and 14 located within the enclosure, a central barrier panel 16 lying 
between the screens 12 and 14 and oriented perpendicularly to the plane of 
said co-planar image screens, a plurality of fixed isolation louvers 20 
located on one face of the enclosure 10 and lying generally in a plane 
parallel to the plane of the screens 12 and 14. In order to view the 
images on the screens 12 and 14, a viewer will generally position him or 
herself along an imaginary center line CL generally aligned with the 
central barrier panel 16 of the enclosure 10. In this way, the right eye R 
of the viewer will have a generally unobstructed viewing path to see the 
image on the screen 12, while the left eye L of the viewer has a similarly 
unimpeded view path to see the image on screen 14. The louvers 20, 
however, prevent crossover viewing so that the image on the screen 14 is 
isolated from the right eye R, while the image on screen 12 is isolated 
from the left eye L. 
The images on screens 12 and 14 may be still or moving, and in both cases 
will be stereoscopic images which define a three-dimensional image for the 
viewer. The method for presenting the images is not critical, and will 
generally comprise either a film projection system or an electronic video 
projection system. Such systems are well known in the art and need not be 
described further herein. 
The isolation louvers 20 are intended to allow the viewer to step back from 
the enclosure 10 without the loss of isolation between the images on 
screens 12 and 14. As illustrated, louvers 20 are parallel to each other 
and aligned on a flat viewing plane 26. It is contemplated, however, that 
the louvers 20 may be arranged, in a non-parallel manner and aligned on a 
curved viewing plane to enhance the image isolation to prevent crossover 
vision. Conveniently, the louvers 20 may be oriented to lie parallel to 
the vision lines 22 from the desire eye. Such alignment, however, is not 
always necessary, and is effective only when it is known the likely 
distance at which the viewer will be positioned. The further back the 
viewer will sit, the less need there is to orient the louvers 20 in a 
non-parallel manner. 
The size and spacing of the louvers 20 will depend primarily on the screen 
(image) sizes and the expected distance back from the enclosure at which 
the viewer(s) will be positioned. Typically, louvers will have a width in 
the range from about 0.5 to 5 inches, more usually from about 1 to 2 
inches, and a spacing between adjacent louvers in the range from about 0.2 
to 1.0 inches, more usually from about 0.5 to 0.7 inches. Viewers may then 
be positioned back from the enclosure 10 by a distance generally in the 
range from about 3 to 50 feet, more usually in the range from about 5 to 
25 feet. 
Referring now to FIG. 2, a system for allowing a viewer to observe 
sequential images projected on a common screen comprises a screen 30 and a 
plurality of movable louvers 32. The louvers 32 are positioned in front of 
the screen and are able to pivot about fixed points 34 which are generally 
located a distance d from the screen 30. Means (not illustrated) are 
provided for simultaneously moving the louvers 32 back and forth between a 
left viewing position shown in full line and a right viewing position 
shown in broken line. When the louvers 32 are all oriented in their left 
viewing position, the left eye L of the viewer is able to view the screen, 
while vision by the right eye R is blocked. Conversely, when the louvers 
32 are in their right viewing position (broken line), the viewer is able 
to observe the screen through the right eye only, and vision from the left 
eye is blocked. 
While FIG. 2 illustrates mechanical louvers, it will be appreciated that 
other systems for alternately blocking the right and left sight lines will 
also find use. For example, liquid crystal barriers (not illustrated) may 
be fixedly aligned in both the left and right louver positions illustrated 
in full and broken line positions in FIG. 2. Then, by alternately 
energizing the right and left liquid crystal barriers, operation of the 
viewing system may be effected in a manner analogous to that described 
above. 
Three-dimensional images are thus obtained by sequentially presenting right 
and left stereoscopic views onto the screen 30 synchronously with the 
shifting of the louvers 32 between their right viewing and left viewing 
positions, respectively. The frequency of presenting the images should be 
greater than 10 images/second, usually being greater than 24 
images/second, in order to maintain continuity of the images. It will be 
appreciated that both film projection systems and electronic video screens 
may be adapted to present the sequential images in a well known manner. 
The dimensions of the movable louvers 32 will depend upon the size of the 
viewing screen 30 as well as the expected distance from the screen of the 
viewer. Typically, the louvers will have a width in the range from about 
0.5 to 5 inches, more typically from about 1 to 2 inches, and will be 
spaced by a distance in the range from about 0.2 to l.0 inches, more 
typically from about 0.5 to 0.7 inches. Viewers may then be positioned a 
distance back from the screen generally in the range from about 3 to 50 
feet. 
With the system of FIG. 2, it will be appreciated that viewers need not 
necessarily be located on or near the center line of the screen (not 
illustrated). Instead, by adjusting the particular angles through which 
the movable isolation louvers 32 are swept, viewers at various locations 
relative to the screen may be accomodated. 
Although the foregoing invention has been described in some detail by way 
of illustration and example for purpose of clarity of understanding, it 
will be obvious that certain changes and modifications may be practiced 
within the scope of the appended claims.