Note: Descriptions are shown in the official language in which they were submitted.
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Split Image Stereoscopic System And Method
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a system and method of
stereoscopic imaging, and in particular to a stereoscopic
system and method in which the left and right eye images
are separately displayed before interlacing so that they
can be more easily polarized. This is made possible by
using a microprism sheet to interlace the separate
oppositely polarized images.
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2. Description of Related Art
The present invention provides various improvements
on the concept of using microprism sheets to interlace
images in a stereoscopic imaging system, as disclosed in
copending U.S. Patent Application Ser. No. 09/481,942. The
improvements include the identification of additional image
sources to which the interlacing arrangements may be
applied, modifications of the microprism sheets that are
used to interlace the images, and integration of the image
interlacing arrangements into stereoscopic video devices
that can be used as handheld video game players, visors,
and the like.
The invention offers a solution to a number of
technical difficulties that have heretofore limited
stereoscopic or "3D" devices to unappealing novelty items,
implemented in the form of cardboard glasses with blue and
red cellophane lenses distributed at fast food restaurants .
Tn particular, the invention makes it possible to use
polarizers and polarizing filters rather than color filters
to distinguish between left and right eye images by
providing a simple way of combining or interlacing the
images following polarization, without the need for beam
splitters or other sophisticated optical or opto-electronic
systems.
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The basic principles of stereoscopic imaging are well-
known. Human vision is stereoscopic because each eye views
the same scene from a different angle. The two separate
images are combined by the brain to create a stereoscopic
effect. In order to recreate the stereoscopic appearance
of a scene on a flat screen, the scene must be captured by
two cameras, one representing what a left eye would
normally see, and one representing what a right eye would
normally see. The left and right eye images are then
interlaced so as to originate from the same location. A
stereoscopic or three-dimensional image is obtained when
each eye sees only the corresponding left and right eye
portions of the interlaced image.
There are two ways to optically modify the left and
right eye portions of the interlaced images so that the
left eye sees only the left eye portion of the interlaced
image and the right eye sees only the right eye portion of
the interlaced image. One way, illustrated in Fig. l, is
to color the left and right eye portions of the interlaced
image 100 and to use color filters 101,102 to ensure that
the left and right eyes see only the correspondingly
colored portions of the interlaced image. The other way to
modify the left and right eye images so that each eye will
only see appropriate portions of the interlaced image is to
polarize the left and right eye images in opposite
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directions, and to use oppositely polarized lenses to view
the oppositely polarized portions of the interlaced image.
Polarization has significant advantages over color
filtering in that it permits the stereoscopic image to be
viewed in natural color without the loss of brightness
caused by color filtering. Natural color is in general
more pleasing to the viewer, while the increased brightness
provided by polarization permits the use of lower intensity
image sources such as LCD displays of the type used in
portable handheld video game players.
In addition, polarization has the advantage that a
person wearing polarized lenses can turn away from the
interlaced image and view other objects or persons without
having to take off the lenses. Since the polarizers and
polarizing lenses are transparent, the stereoscopic effect
can be created with what appears to the viewer to be
ordinary clear lenses, as opposed to the color lenses used
in conventional non-polarizing stereoscopic systems.
Despite the well-known advantages of using polarizing
filters to distinguish the left and right eye portions of
interlaced stereoscopic images, it is currently impossible
to use polarization in connection with conventional cathode
ray tube or LCD displays because the light emitting pixels
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of the displays cannot be made to emit polarized light. As
a result, unlike stereoscopic displays that use color,
which can be colorized and interlaced before recording or
broadcast, stereoscopic displays that use polarization
require that polarization be carried out at the viewing
location and, in addition,.require that interlacing also be
carried out at the viewing location since it is virtually
impossible to synchronize or align oppositely polarized
sheets with the appropriate portions of an image that has
been broadcast or recorded in interlaced form. It is not
so much the lack of viable polarizers or polarizing filters
that has limited the available of polarizing stereoscopic
systems, but rather the lack of a practical image
interlacing arrangement for interlacing the images
following polarization.
By way of background, examples of image interlacing
arrangements using relatively complex or expensive optical
devices such as beam splatters are disclosed in U.S. Patent
Nos. 5,671,992, 5,993,004, and 5,956,180, while a
stereoscopic device utilizing multiple polarizing sheets is
disclosed in U.S. Patent No. 5,973,831. In addition, a
number of arrangements have been proposed for
electronically synchronizing polarizers with temporally
interlaced images, z.e., for switching polarization as the
left and right eye images are alternately displayed, but
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such systems are even more complex than purely optical
arrangements.
The present invention, on the other hand, provides a
simple and convenient solution to the problem of
interlacing images at the viewing location, making possible
practical stereoscopic devices that use polarization
instead of color filtering, offering a dramatic improvement
over the throw-away stereoscopic effects arrangements
currently .in use, and a practical alternative to the
complex optical or opto-electronic systems proposed in
previous patents.
SUMMARY OF THE INVENTION
It is accordingly a first objective of the invention
to provide a practical way of optically interlacing
separate left eye and right eye portions of a stereoscopic
image, so that the separate portions of the image can be
more conveniently recorded or broadcast, and subsequently
polarized, as separate images.
It is a second objective of the invention to provide
arrangements for interlacing images in a stereoscopic
imaging system that can be used with a variety of different
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image sources, including split screens, multiple screens,
and combinations of video and static displays or objects.
It is a third objective of the invention to provide a
practical arrangement for interlacing oppositely polarized
left and right eye images for use in stereoscopic imaging
systems and devices.
It is a fourth objective of the invention to provide
microprism sheets having improved ability to focus or
direct light to a desired location, and which may be used
to interlace images.
It is a fifth objective of the invention to provide a
projection screen that serves to interlace images.
It is a sixth objective of the invention to provide a
handheld device for viewing stereoscopic video images in
true color without loss of brightness, and that can be used
with an LCD display.
These objectives are achieved, in accordance with the
principles of various preferred embodiments of the
invention, by providing a stereoscopic imaging system and
method in which left and right eye images are separately
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transmitted to a display device, polarized following
display, and combined following polarization.
Image interlacing is providing by an especially simple
and effective arrangement involving a microprism sheet
having one set of surfaces oriented at a first angle
corresponding to a position of a first image source, and a
second set of surfaces oriented at a second angle
corresponding to a position of a second image source so as
to interlace the images. By appropriately selecting the
position of the images to be interlaced, and therefore the
first and second angles, the interlaced image can be made
to project into a single plane. If the images are pre-
polarized or otherwise differentiated before interlacing,
the interlaced images can thus be directly combined to
exhibit a three-dimensional stereoscopic effect when viewed
directly through corresponding lenses.
The separate images combined or interlaced in the
preferred stereoscopic imaging system and method of the
invention may be displayed on a split screen, multiple
screens arranged horizontally, multiple screens arranged
vertically, and may even include images of real objects, as
well as images displayed on cathode ray tubes, liquid
crystals displays, or any other video or still image
displays.
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The arrangement of the invention can be used to make
an especially simple and yet effective stereoscopic viewing
device. Because the invention permits polarization to
distinguish left and right eye images, there is no loss of
brightness and a relatively dim liquid crystal display can
be used as the source of the left and right eye images. The
result is a stereoscopic device having a construction that
is significantly simpler than the stereoscopic viewing
devices or visors of the prior art, which relied on beam
splatters or multiple polarizations. Such a stereoscopic
device has potential application as a video game player,
virtual reality display visor, stand-alone "3D" movie
viewer, and so forth.
While especially suitable for use in stereoscopic
imaging systems or devices, and in particular those in
which the left and right eye portions of a stereoscopic or
three-dimensional image are distinguished by opposite
polarization, it will be appreciated by those skilled in
the art that the image interlacing arrangements of the
invention may be used in contexts other than those
involving true stereoscopic images, including heads-up
displays of various types, closed captioning, or other
displays of superimposed images.
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Tn addition to planar microprism sheets disclosed in
the parent application, U.S. Patent Application Ser. No.
09/481,942, it is also possible, according to further
embodiments of the present invention, to vary the
construction of the microprism sheets by varying the shape
of individual facets, or by curving the sheets to change
the direction of light transmission. Although potentially
useful in the context of image interlacing, it will be
appreciated by those skilled in the art that this aspect of
the invention may be used in a wide variety of microprism
applications, including image focusing and projection
arrangements in general.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. l is a schematic diagram of a prior art
stereoscopic imaging arrangement.
Fig. 2 is a schematic diagram illustrating use of a
microprism sheet to interlace images according to the
principles of a first preferred embodiment of the
invention.
Fig. 3 is a schematic diagram showing a handheld
stereoscopic device constructed according to the principles
of a second preferred embodiment of the invention.
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Fig. 4 is a schematic diagram of an image interlacing
arrangement according to a third preferred embodiment of
the invention.
Fig. 5 is a schematic diagram of an image interlacing
arrangement according to a fourth preferred embodiment of
the invention.
Fig. 6 is a schematic diagram of an image interlacing
arrangement according to a fifth preferred embodiment of
the invention.
Figs. 7A-7C are plan views of modifications of the
microprism sheets shown in Figs. 2-6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As illustrated in Fig. 2, a microprism sheet 1 is
arranged such that light from a first image 2 is refracted
by surfaces 3 and light from a second image 4 is refracted
by surfaces 5 so as to exit the microprism sheet in
parallel and thereby form a single interlaced image 6. The
angles of surfaces 3 and 5 are selected based on the
position of the microprism and on the relative positions of
the separate images, which originate in this embodiment
from a split screen divided vertically, horizontally, or in
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any other desired manner, so that the separate images,
which may correspond to the above-described left eye and
right eye images, can easily be polarized by polarizing
filters or sheets 7,8 positioned between the image source
and the microprism sheet before interlacing for viewing by
appropriately polarized lenses 9,10 after interlacing.
It will be appreciated that the facets of the
microprism sheet 1 illustrated in Fig. 2 are not drawn to
scale. The construction of the microprism sheet may be
entirely conventional, utilizing the known construction
techniques and materials described in copending U.S. Patent
Application Ser. No. 09/481,942, or the microprism sheet
may be modified to include anti-glare, anti-radiation, or
other coatings. In addition, according to the principles
described in the copending application, the separate
polarizers 7 and 8 may even be replaced by polarizing
coatings on individual facets of the microprism sheet 1.
The simple image interlacing arrangement illustrated
in Fig. 1 can easily be integrated into stereoscopic
effects devices such as the one illustrated in Fig. 3. In
this device, the image source is provided by an LCD screen
11, polarization by polarizing sheets 12,13, interlacing by
microprism sheet 14, and direction of the appropriate image
portions to the left and right eyes of the viewer by
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eyepieces 15,16 including polarized filters or lenses
17,18, all of which are contained in a housing 19. In
addition, it is within the scope of the invention to
provide additional optical components (not shown) for the
purpose of focusing or guiding light between the
illustrated components.
The stereoscopic effects device of this embodiment of
the invention can be used as a portable or handheld video
game player, or integrated into a variety of other devices
such as arcade games, virtual reality visors, aircraft or
military training simulators, and any other devices that
currently use flat two-dimensional displays, but which
might benefit from the addition of stereoscopic effects.
Instead of a single screen image source as illustrated
in Fig. 2, the principles of the invention may be extended
to cover images that originate on separate screens 20,21,
as illustrated in Fig. 4, or arbitrary image sources 22
other than video screens, including real objects, as
illustrated in Fig. 5. In addition, by placing a
microprism sheet 23 having appropriately shaped facets in
front of a mirror 24, or by adding a reflective coating to
the back of the sheet, the image interlacing arrangement
can possibly be arranged to form an image interlacing
projection screen, as illustrated in Fig. 6.
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Finally, as illustrated in Figs. 7A-7C, the microprism
sheets used to interlace the images in any of the
embodiments of Figs. 2-4 need not be planar microprism
sheets with uniform facets. It is also within the scope of
the invention to vary the size of the facets so as to focus
or project images transmitted thereby, as illustrated in
Fig, 7A, to curve the sheets to achieve similar effects, as
illustrated in Fig. 7B, or to combine the concepts of
varying the size of the facets and curving the sheets, as
illustrated in Fig. 7C.
Although potentially useful in connection with image
interlacing applications as described herein, the
microprism sheet modifications illustrated in Figs. 7A-7C
may be used in any context in which microprism sheets are
conventionally used, and possibly in additional contexts.
For example, if the microprism sheet of Fig. 7B is formed
in a parabola shape, the microprism sheet can be used as a
convenient focusing lens or collimator.
Having thus described a preferred embodiment of the
invention in sufficient detail to enable those skilled in
the art to make and use the invention, it will nevertheless
be appreciated that numerous variations and modifications
of the illustrated embodiment may be made without departing
from the spirit of the invention. Accordingly, it is
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intended that the invention not be limited by the above
description or accompanying drawings, but that it be
defined solely in accordance with the appended claims.
