Stereoscopic apparatus and method of using same

A light weight, compact, stereoscopic apparatus in the form of a lens assembly that can be removably attached to a conventional still motion picture or television camera as an integral unit in place of the normal lens so that a camera may be conveniently converted to three dimensional photography. The lens assembly when used results in superimposed stereoscopic records in color, which superimposed records are of the same size, and when viewed through suitably selected filters are in full relief and color, but when viewed without filters appear as a conventional two-dimensional view.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
Stereoscopic Apparatus and Method of Using Same. 
2. Description of the Prior Art 
A number of optical systems have been developed in the past to produce 
stereoscopic views of a scene. The most practical methods employ means to 
produce individual records which were made from two laterally displaced 
positions, generally 2.5 inches apart. This distance corresponds roughly 
with the human interocular. The records are viewed by suitable means 
whereby the right eye sees only the right record and the left eye sees 
only the left record. The resulting effect is a stereoscopic perspective 
view of the scene. It is important to understand that each of the two 
records is different from the other by virtue of position relative to the 
eyes of a human in order that a true stereoscopic view of the scene be 
presented to the brain. The majority of inventions produced have dealt 
with methods to record and present these two distinct records to each eye 
for viewing. Generally, two methods are used to carry out the stereoscopic 
technique. One method uses separate picture taking means such as separate 
cameras. Then separate viewing means are used. The other method is a 
variation on the first which may utilize a composite technique at any of 
various points in the process. As an example, a single camera may be 
equipped to make both records or a single strip of film may be used, or in 
the case of a television system, a picture tube is used to present the 
separate views with suitable optical means to channel each record to the 
appropriate eye. 
Several problems are common to all methods. Unique distortions not found in 
two-dimensional technique may be created at any point in the stereoscopic 
process so as to present a stereoscopic view of the scene of improper 
perspective. Most notable are those distortions produced by unequal 
optical paths to each record, improper camera interaxial IE, lens 
separation, poor vertical registration, and cross-talk, a condition 
whereby each eye may also see part of the image intended for the other 
eye. Varied amounts of these distortions seem to greatly affect the 
quality of the stereoscopic view. 
The most popular method of composite film or television recording means has 
been the application of a prism or mirror assembly in front of the lens of 
a single camera. The prisms or mirrors present two distinct and separate 
views of the scene to the lens. The apparent viewing positions may be 
spaced about 2.5 inches apart. The image presented to the lens may be a 
coded composite view such as achieved by the application of filter means, 
or the image may be two adjacent views spaced laterally or vertically. The 
particular problems with this technique are that the image may suffer from 
unequal path lengths which make one record appear as though it was made at 
a point closer to the scene. This is a very noticeable distortion. Also, 
only lenses of moderate to long focal length can be used due to the 
limited aperture of the front reflector optics. 
A primary object of the present invention is to provide a lens assembly 
that may be mounted on a conventional camera used in producing two 
dimensional views and transform the latter to one in which each of the 
stereoscopic records is of substantially the same size, and the invention 
employing lenses of short focal lengths such as used in normal production 
without vignetting the record. 
Still another object of the invention is to provide a method of adjusting 
horizontal displacement of the aforementioned record pairs relative to 
each other, thereby providing convergence adjustment means to the camera 
operator so as to control the degree of relief in the picture, said 
adjustment means allowing the taking of stereoscopic pictures that may be 
viewed in three-dimensions with suitable filter means or as simultaneous 
conventional two-dimensional pictures. 
It is yet another object of the present invention to provide a system of 
three-dimensional color television signals. 
Still another object of this invention is to provide adjustment means to 
control the ratio of luminosity of each record to the other so as to 
provide a color rendition of wide spectral range and deep saturation not 
possible with previous composite color three-dimension methods. 
SUMMARY OF THE INVENTION 
The stereoscopic apparatus of the present invention replaces the lens of a 
conventional still, motion picture, or television camera. No further 
modification is necessary. The stereoscopic apparatus may consist of two 
similar lenses placed in front of an equal path mirror/prism beam 
splitting assembly which is attached to the camera body. Suitable filter 
means which pass equal amounts of the light spectrum are interposed in the 
light beams to code the two images. The filters may be color complementary 
or polarizing depending on the recording medium. Suitable glasses or 
screens equipped with filters similar to those used in recording may be 
used to view the scene in three-dimensions. Additionally, neutral density 
filters may also be interposed to control luminosity of the individual 
beams thereby presenting a view in full color and eliminating a condition 
known to those familiar to the art as "retnal rivalry". Specific adjusting 
means are provided in various embodiments of the invention to control 
image displacement and lens toe-in.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A first form A of the stereoscopic apparatus is shown in FIG. 1 that 
includes a rearwardly disposed flange 30 that have a plurality of spaced 
key hole shaped opening 32 therein that may have pins 34 that support 
heads 36 extended therethrough. The pins 34 extend forwardly from an 
opaque housing B that may be a part of a conventional still, motion 
picture, or television camera. The pins 34 and heads 36 serve to removably 
support a lens assembly (not shown) on the housing B to permit two 
dimensional pictures to be taken, but when the lens assembly is removed, 
the pins 34 and heads 36 serve to removably secure the stereoscopic 
apparatus A to the housing B in communication with an opening 38 in the 
housing B. When the pins 34 and heads 36 are extended through openings 32 
and the apparatus A rotated slightly relative thereto, the apparatus A is 
removably supported on housing B. 
Apparatus A as may be seen in FIG. 1 includes first and second lens holders 
1 and 2 in which first and second lens 1a and 2a are mounted that admit 
first and second separate bundles of light rays 3 and 4, representing left 
and right perspective views of the scene. For simplicity of illustration 
the first and second bundles of light 3 and 4 are depicted in FIG. 2 as 
single lines. 
First light rays 3 after passing through lens 1a proceed through a first 
filter pack 5. Second light rays 4 after passing through second lens 2a 
proceeds through a second filter pack 6. The first filter pack 5 may be of 
a color complementary filter such as the color cyan, and a neutral density 
filter to control the luminosity of first rays 3 relative to second rays 4 
as the latter passes through second filter pack 6. First and second filter 
packs 5 and 6 may be placed forwardly of the first and second lens 1a and 
2a without departing from the method in which the present invention is 
used. 
First light rays 3 continue into a generally cubic glass block 7 and a 
first prism 8 that is in abutting contact therewith. The hypotenuse 8a is 
silvered to reflect first light rays 3 ninety degrees to a second prism 12 
that is secured to the first prism 8. The first prism 8 has a second prism 
9 in abutting contact therewith, and the second prism having a second 
hypotenuse 9a that is in contact with a third hypotenuse 12a of a third 
prism 12. The second and third hypotenuses 9a and 12a are semi-silvered to 
reflect first light rays at ninety degrees onto light sensitive recording 
means D. The back focal length of first lens 1a by means later to be 
described is adjusted to form a real image on recording means D. 
The distance first rays 3 traverse after entering first lens 1a to the 
recording means D is substantially the same as that traveled by the second 
rays 4. The first and second lens 1a and 2a may be of short focal length 
such as those used in normal production, and without vigenetting the 
images produced on the recording means D. 
Concurrently with the passage of first light rays 3 through the first lens 
1a, second light rays 4 pass through the second lens 2a. Second light rays 
4 after passing through second lens 2a continues through a second filter 
pack 6 that is a complement to first filter pack 5. 
The filter in second filter pack 6 may be red-orange and if desired may 
also include a neutral density filter to control luminosity of second rays 
4 relative to first rays 3. 
The second rays 4 after passing through the second filter pack 6 enter a 
parallelogram shaped block of glass 10 that has parallel sides 10a and 10b 
as best seen in FIG. 2. The sides 10a and 10b are semi-silvered to reflect 
the second light rays 4 ninety degrees into the third prism 12. The 
semi-silvered surfaces on the hypotenuses 9a and 12a allow second rays 4 
that have been reflected thereto from the silvered side 11 to pass to the 
recording means D. The back focal length of the second lens 2a has been 
adjusted by means later to be described to form a real image on the 
recording means 14. The parallelogram shaped block 10 and the third prism 
12 should have the same index of refraction as the glass block 7 as well 
as the second prisms 8 and 9 whereby the separate images produced by the 
first and second light rays 3 and 4 from the first and second lens 1a and 
2a are of equal size. Housing B includes a conventional shutter C. The 
semi silvered surfaces of the hypotenuses 9a and 12a allow the second 
light rays 4 to pass therethrough. The above-described optical arrangement 
reduces annoying image size disparity, aniseikonia, and it also allows the 
use of lenses of short focal length which were heretofor not possible with 
conventional lens/prism optical systems. The use of lenses 1a and 2a of 
short focal lengths result in a greater depth of field for a given light 
level, as well as greater depth perspective than is possible with fixed 
interaxial embodiment. 
An assembly E serves to hold all the optical elements above described, with 
the exception of first and second lens 1a and 2a, in a fixed position 
relative to one another. The assembly E, by use of the flange 30 that 
forms a part thereof, may after a two-dimensional lens unit (not shown) is 
removed from camera housing B, may be mounted on the camera housing and 
transform the latter to one that concurrently records first and second 
images on the light sensitive means D due to the first and second bundles 
of light rays 3 and 4 impinging on the latter. 
The assembly E that permits the optical elements previously described to be 
mounted on the housing B in light communication with the opening 38 
therein may take various forms and shapes. Assembly E is formed from an 
opaque material such as a suitable polymerized resin or the like. In FIG. 
2 the assembly E is illustrated as including a conical shell 40 that 
extends outwardly from the ring-shaped flange 30, with the shell having 
threads 42 on the free end thereof that are engaged by threads 46 defined 
on a circular shell 44. 
The shells 40 and 44 are in conjunction with a transverse web 48 that forms 
a part of the latter and spacer blocks 49, 49a, 49b shown in FIG. 2 
support glass block 7 and parallelogram shaped block 10 in fixed 
relationship with one another. A first circular boss 50 projects forwardly 
from web 48 and is axially aligned with block 7 as shown in FIG. 2. The 
outer end of first boss 50 has threads 52 defined on the outer end thereof 
that engage threads 56 formed on a first collar 54. The first collar 54 
has threads 58 formed on the forward end thereof. A circular rib 60 
extends inwardly in first collar 54 and has a peripheral portion of the 
first filter pack 5 resting thereon. 
The lens holder 1 includes a cylindrical shell 62 that has a pin 64 
extending inwardly therefrom that slidably engages a helical groove 66 
defined on the exterior surface of collar 54. An externally threaded ring 
71 engages threads 58 and serves in conjunction with rib 60 to removably 
support first filter pack 5 in first lens holder 1. A second collar 72 is 
provided that has threads 70 defined on the interior thereof that engage 
threads 68 on the forward extremity of lens holder 1. Collar 72 includes 
an inwardly extending lip 74 that grips the peripheral edge of first lens 
1a. When the lens holder 1 is rotated relative to collar 54 the first lens 
1a is moved longitudinally relative to the light sensitive recording means 
D. The second lens holder 2 is supported from a second boss 50' that 
projects forwardly from web 48 by a second structure that is the same as 
the first structure above described in conjunction with the first lens 
holder 1. The components used in supporting the second lens holder from 
frameword 48 are identified by the same numerals used in describing the 
supporting elements for the first lens holder 1 but with primes added 
thereto. The lateral spacing between the centers of lens holders 1 and 2 
is preferably substantially two and one-half inches. 
From the above description of the first form A of the invention it will be 
seen that a portable unit is provided that may be readily used to convert 
a still, motion picture, or television camera that includes a housing B 
and that is used for taking two dimensional views into a stereoscopic 
camera used for taking three dimensional views with a minimum of 
alterations of the structure of the camera. When the invention A is used 
in the manner above described the resulting records on the light sensitive 
means D may be alternately viewed through suitably selected filters in 
full relief and color, or viewed without filters as a conventional 
two-dimensional view. 
Referring now to FIG. 3 where a second form A-1 of the apparatus is 
illustrated, the light paths are substantially the same as those in FIG. 
1, supplementary lenses 14, 16 and 17 are introduced to allow the 
preferred use of conventional camera lenses of fixed back focal length 
such as may be found on various still, motion picture, or television 
cameras. Supplementary lens 15 may be focused at the back image plane of 
lens 1a, thereby causing beam 3 to become collimated and pass through 
block 7 and prisms 8 and 9 to supplementary lens 17 as parallel light. 
Supplementary lens 17 then brings beam 3 to focus on image recording means 
D. 
Substantially the same process takes place with beam 4, which, after 
passing through lens 2a and filter pack 6 is collimated by supplementary 
lens 16 and passes through prisms 10, 11, 12 and 9 where beam 4 is focused 
onto image recording means D by supplementary lens 17. The application of 
supplementary lenses 14, 16 and 17 inverts the image. In a normal motion 
picture or television camera, the image is also inverted by lenses that 
may be similar to lens 1a or 2a. The net effect of the optical system of 
FIG. 3 might be that no inversion of the image takes place. Further 
modification of the camera might be necessary to reduce the system of FIG. 
3 to practice but for the application of simply changing prism 8 to a roof 
or amiciprism in the case of beam 3 and also changing prism 10 or 11 to a 
roof or amici prism for beam 4 to reinvert the image on image recording 
means 14. 
The optical elements in the second form A-1 of the invention are held in 
desired spaced relationship by the assembly E that is modified in 
conventional manner to support the supplementary lens 15, 17 and 17. 
Referring now to FIG. 4 for a third form A-3 of the invention, a screw 18 
and carrier 19 are introduced as a lens interaxial/convergence control 
assembly to adjust depth content of the stereoscopic view. Lens 1a, filter 
pack 5, and lens 15 are mounted on a carrier 19 that is adjustably and 
laterally movable relative to assembly E on which is mounted by 
conventional means. It is not necessary for filter pack 5 to be mounted on 
carrier 19, however it may become convenient when the invention is reduced 
to practice. In practice, screw 18 is rotated and comes to bear on carrier 
19 and moves it toward lens 4 causing beam 3 to move closer to beam 4 at 
image recording plane 14. The net effect will be to reduce the depth in 
the resulting stereoscopic view. Of course, lens 2a, filter pack 6 and 
lens 16 may also be moved relative to lens 1a and produce the same results 
at image recording plane D. Screw 18 may also be affixed to cause carrier 
19 to rotate about the axis of beam 3 to "toe-in" the lenses. Lens toe-in 
produces a small amount of keystone distortion of the resulting image and 
should be avoided. 
In practice, the lens interaxial/convergence adjustment of screw 18 and 
carrier 19, together with the focal length of lenses 1a and 2a determine 
lens convergence. If some other convergence point is desired, then either 
focal length or interaxial may be adjusted. Lens toe-in may also be used. 
To achieve records which may be viewed in two-dimensions as well as 
three-dimensions with the subject invention, it is a simple matter to 
adjust knob 18 and cause carrier 19 to move lens 1a relative to lens 2a 
while viewing the resulting images in a camera finder. If significant 
image disparity or "fringing" is noted, then it is a simple matter to 
adjust the focal length of lenses 1a and 2a to reduce this disparity. This 
fringing may not be eliminated completely due to the slight separation of 
lenses 1a and 2a, nor is it desirous in as much as a condition of no image 
disparity or zero fringing is only two-dimensional and devoid of any depth 
cue information. Ideally, filter pack 5 must not pass any light in the 
bandpass of filter pack 6 or cross-talk between channels will be seen. 
However, recent researches by Dr. Edwin Land suggest that a richer color 
rendition may be achieved if equal amounts of complementary colors reach 
image recording means. The specific application of neutral density filters 
at filter pack 5 and 6 control color luminosity ratios. Considerable 
research into Land's work by the inventor suggest that empirically derived 
amounts of cross-talk between color channels may further improve color 
rendition and in the preferred embodiment of the invention may occur in 
the region of the color yellow. Therefore, filters 5 and 6 are not sharp 
cut-off, but provide a measured amount of cross talk dependent on the 
media used at image plane D and the viewing means employed. 
The use of measured amounts of cross-talk restore luminescence levels in a 
color television transmission system to produce a compatible 
two-dimensional picture when viewed in black and white. Reduced interaxial 
and adjusted lens focal lengths may also achieve a compatible 
two-dimensional color television picture of reduced depth with the subject 
invention. If normal stereoscopic perspective is maintained, then an 
excellent three-dimensional color television picture is produced, however 
black and white versions of the picture may suffer due mostly to 
cross-talk of luminescence information. To improve two-dimensional viewing 
in black and white, the red pick-up camera tube of the color television 
camera must not be allowed to contribute to the luminescence information 
channel by matrix adjustment or filter means or, in the case of 4 tube 
cameras, a cyan filter may be simply interposed in the luminescence 
derived light beam and the tube gain adjusted. 
The use and operation of the inventions have been described previously in 
detail and need not be repeated.