Projected volume display system and method

A method of viewing a three dimensional display and structure therefor which comprises providing a three dimensional display, providing a projection surface which is a sector of a substantial spheroid, providing projection optics projecting the three dimensional display onto the projection surface and placing an observer within the substantial spheroid. In accordance with a second embodiment there is provided a method of viewing a three dimensional display comprising providing a double parabolic mirror, providing a three dimensional display within the double parabolic mirror, projecting an image of the three dimensional display external of the parabolic mirror and viewing the image from a location external of the double parabolic mirror.

CROSS-REFERENCE TO COPENDING APPLICATIONS 
This application is an improvement of copending application Ser. No. 
07/584,413, filed Sep. 17, 1990, now U.S. Pat. No. 5,042,909, the contents 
of which are incorporated herein by reference. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a three dimensional display system and, more 
specifically, to a system for transferring and projecting a three 
dimensional image onto a screen or into space remote from the original 
three dimensional image. 
2. Brief Description of the Prior Art 
In accordance with the above noted copending application, a disk-like 
screen is connected to the end of a motor shaft. The disk is attached to 
the shaft of a motor at a 45 degree angle or compound helix shape, though 
this angle can be varied to provide a larger or smaller height or z-axis 
dimension, so that, as the disk rotates, a displacement of any given point 
thereon along the z-axis takes place. The image is formed on the screen by 
projecting a light beam, such as from a laser, through a modulator and 
toward a scanner which produces an x-y scan of the beam on a screen, the 
screen being the disk discussed hereinabove. The disk can be translucent, 
such as lucite, so that images can be projected thereon onto the front 
and/or rear surfaces thereof. The modulation or strobing of the scan is 
then synchronized with the rotating disk by control of the motor speed so 
that a three dimensional pattern appears on the screen. It can be seen 
that any point on the x-y scan from the scanner which impinges upon the 
screen will move along a z-axis direction since the screen or disk at that 
point produces such z-axis movement. This movement of the displayed image 
provides the three dimensional effect. The adjustment of the angle between 
the disk surface and the x-y plane of the scanned x-y image will determine 
the z-dimension or height of the three dimensional image, the disk angle 
being adjustable on-line, if so desired. 
While the disk is a planar opaque screen for receiving a scanned image 
thereon on one surface thereof, the screen can take many other forms. For 
example, the disk can be translucent, such as lucite, and thereby be 
capable of receiving a scanned image thereon on both major surfaces. The 
lucite disk can be in the form of a pair of angularly truncated cylinders 
with the same truncation angle which fit together at the angularly 
truncated surfaces to form a new cylinder wherein the surfaces at which 
truncation takes place are translucent. In addition, the screen can take 
on shapes other than planar, it merely being necessary that at least some 
portion thereof move in the z-direction during rotation thereof while 
projection of the x-y image thereon takes place to provide the three 
dimensional image. As a further embodiment, the disk can be placed in a 
gas filled or evacuated CRT with the image impinging thereon being the 
scanned beam of the tube. Phosphors can be disposed on the disk which, 
when excited, will form the three dimensional image. As a still further 
embodiment, the screen can be planar and disposed normal to the projected 
x-y image. The three dimensional affect is then provided by moving the 
entire screen along the z-axis in synchronism with the scanned x-y image 
to provide the three dimensional affect. A cam driven shaft attached to 
the screen can provide such screen movement along the z-axis. 
While the above described prior system provides a highly effective 
three-dimensional display, the fact that the display is so closely 
positioned with respect to the rapidly rotating disk makes it undesirable 
and dangerous for observers to be located close to the display. In 
addition, the display cannot be readily observed when the ambient light is 
significant. Accordingly, for example, if the system were to be used in 
the cockpit of an airplane and sunlight were to enter the cockpit, viewing 
of the display would be difficult if not impossible. It is therefore also 
the desire to provide a three dimensional display of the type described in 
the above noted copending application which can be viewed under almost any 
type of ambient light conditions. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, the above noted problems of the 
prior art are eliminated and there is provided a system which is capable 
of projecting a three dimensional image remote from the points of 
origination of the initial three dimensional image which duplicates the 
original image. In this manner, one can operate directly with the 
duplicated image without the possibility of injury resulting from the high 
speed rotating disk and under substantially any type of ambient light. 
Briefly, in accordance with one embodiment of the present invention, the 
three dimensional formed by the above described prior system is projected 
by projection optics onto a projection surface, preferably in the form of 
a half silvered mirror. The projection surface is preferably a sector of a 
sphere. The observer is located preferably within the sphere and 
sufficiently distanced from the disk to provide viewing of a three 
dimensional image as well as entry therein without incurring the dangers 
inherent from the rapidly rotating disk and the initial three dimensional 
image formed is shielded from ambient light. 
In accordance with a second embodiment of the invention, a pair of 
parabolic mirrors are disposed in contact with each other along their 
circumferences to form a paraboloid. An opening is provided at the center 
of each parabolic mirror. The disk of the above described prior system is 
located within the paraboloid and the signal projected on the disk by the 
x and y scanners is formed into a three dimensional image within the 
paraboloid. This three dimensional image is projection off of the mirrors 
at the interior of the paraboloid through the opening provided at the 
center of the other parabolic mirror to provide a projected virtual image 
external to the paraboloid which can be viewed by a viewer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIGURE there is shown a schematic diagram in accordance 
with a first embodiment of the projected volume display system in 
accordance with the present invention. 
The system includes a laser 1 which projects a light beam through a 
modulator 3 onto an x-y scanner 5. The modulator 3 is externally 
controlled in predetermined manner (not shown) to control the intensity of 
the laser light beam 7 passing therethrough. It is understood that the 
light intensity can be controlled so that no light passes through the 
modulator, when so desired. The x-y scanner 5, whose scanning rate and 
position are controlled by x,y inputs 9 and synchronization electronics 11 
are shown in detail in the above noted copending application. The x-y 
scanner 5 scans the light beam 7 from the modulator 3 along the x-y plane 
and projects this x-y image 13 onto a transparent screen 15, preferably 
polymethylmethacrylate. The screen 15 is in the form of a disk. 
The screen 15 is rotated by a motor 17 under rotary speed control of the 
synchronization electronics 11 via a motor shaft 19 connected to the 
screen to form the three dimensional image 21. The rotary speed of the 
shaft 19 is preferably synchronized with the scanning rate of the scanner 
5. A typical synchronization circuit is shown and described in FIG. 2 of 
the above noted patent application and is incorporated herein by 
reference. The angle of the screen 15 is preferably 45 degrees with 
respect to the direction of the image 13 from the scanner 5, it being 
understood that the z-dimension is a function of the angle of the screen. 
The three dimensional image 21 formed by rotation of the screen 15 is 
projected through projection optics 23 onto a projection surface 25 
whereat a three dimensional projected volume image is provided. The 
projection optics 23 is preferably a convex lens 29 followed by a concavey 
lens 31, it being understood that other lens systems capable of projecting 
the image 21 onto the projection surface 25 can also be used. The 
projection surface is preferably a half silvered-type mirror. 
It can be seen that the rotation of the screen 15 with the x-y image 13 
being projected thereon will result in the three dimensional image 21 as 
in the above noted prior application. This three dimensional image 21 is 
projected through projection optics 23 onto the projection surface 25 
whereat an observer 33 can view the projected three dimensional image 27 
without the dangers inherent in being located adjacent the rotating screen 
15. Also, the observer 33 can be positioned within the projection surface 
25 with the projection surface being shieldable from ambient light. 
Referring now to FIG. 2, there is shown a second embodiment of the present 
invention wherein like numbers represent the same or similar structure to 
that discussed above with reference to FIG. 1. 
The laser 1, modulator 3 x-y scanner 5, x,y inputs 9 and synchronization 
electronics 11 are identical to those of FIG. 1 and provide the x-y image 
13 on the screen 15. The screen 15 is rotated by motor 17 under control of 
the synchronization electronics 11 via shaft 19 as in the embodiment of 
FIG. 1. The screen 15 is disposed within a double parabolic mirror in the 
form of a paraboloid 42 composed of two parabolic mirrors 43 and 45 joined 
together at their perimeters. The parabolic mirror 43 has a centrally 
located aperture 47 through which the x-y image 13 travels onto the screen 
15 which is located within the paraboloid 41. The three dimensional image 
21 is formed within the paraboloid 41 and is projected onto and from the 
parabolic mirrors 43 and 45 and through an aperture 49 centrally located 
in the mirror 45 to form a virtual image 51 of the image 21 external to 
the paraboloid. An observer 53 can then view the virtual image 51 from a 
position remote from the screen 15. 
Though the invention has been described with respect to specific preferred 
embodiments thereof, many variations and modifications will immediately 
become apparent to those skilled in the art. It is therefore the intention 
that the appended claims be interpreted as broadly as possible in view of 
the prior art to include all such variations and modifications.