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Claims  |
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What is claimed as new and desired to be secured by Letters Patent of the
United States is:
1. A holographic display apparatus comprising:
a display device;
means for producing a series of two dimensional projections of an object to
be rendered for a plane which is coincident with a plane of the display
device;
means for producing wavefront interference information, independent of the
object data in the series of two dimensional projections of an object,
relative to an intermediate plane located at a predetermined position
relative to the display device;
means, connected to the means for producing two dimensional projections,
the means for producing wavefront interference information, and the
display device, for combining said two dimensional projections and said
wavefront interference information once the series of two dimensional
projections of an object has been produced; and
means, connected to the display device and the means for combining said two
dimensional projections and said wavefront interference information, for
creating a diffraction grating in said display device based upon a
combination of the two dimensional projections and the wavefront
interference information to thereby provide a holographic image of an
object from a number of positions relative to said display device.
2. An apparatus according to claim 1, wherein said means for producing said
two dimensional projections produces said two dimensional projections
using a ray tracing operation.
3. An apparatus according to claim 1, wherein said display device includes
an electro-optic material and a pair of electrodes disposed in operable
contact with said electro-optic material, and wherein said means for
creating a diffraction grating in said display device includes:
means for transmitting an electrical signal to the pair of electrodes in
response to the combination of the two dimensional projections and the
wavefront interference information; and
means for creating a diffraction grating within the electro-optic material
of said display device in response to said transmitted electrical signal.
4. An image display device having a multilayer structure, comprising:
a processor layer including means, responsive to a series of two
dimensional projections of an object and to wavefront interference
information which is independent of the object data in the series of two
dimensional projections of said object, for combining the two dimensional
projections and the wavefront interference information once the series of
two dimensional projections is provided thereto, said processor layer also
including driving transistors for generating respective driving signals
based upon the combination of the two dimensional projections and the
wavefront interference information;
an electro-optic material layer; and
a plurality of layers disposed between said processor layer and said
electro-optic material layer having through holes with connectors passing
therethrough operably connecting the driving transistors of the processor
layer to the electro-optic material layer such that the driving signals of
the driving transistors create a diffraction grating within said
electro-optic material layer based upon a combination of the two
dimensional projections and the wavefront interference information to
thereby provide a holographic image of an object from a number of
positions relative to said electro-optic material layer.
5. A device according to claim 4, wherein said electro-optic material layer
includes three different color filters for generating a color holographic
image and the electro-optic material layer displays three different
gratings, corresponding to the three different color filters.
6. A device according to claim 4, wherein power is supplied to said
processor layer via through holes in a bottom portion of said processor
layer.
7. A device according to claim 4, wherein power is supplied to said
processor layer via power rails mounted on a transparent layer disposed on
top of the electro-optic material layer.
8. A device according to claim 4 further comprising means, operably
connected to said processor layer, for optically receiving data related to
the series of two dimensional projections of an object.
9. A device according to claim 4 wherein said plurality of layers disposed
between said processor layer and said electro-optic material layer
comprises a first optical interface layer which includes at least one
electrode for electrically connecting a respective driving transistor of
said processor layer to said electro-optic material layer.
10. A device according to claim 9 wherein said first optical interface
layer comprises a plurality of transparent electrodes for electrically
connecting respective ones of the driving transistors of said processor
layer to said electro-optic material layer.
11. A device according to claim 9 wherein said plurality of layers disposed
between said processor layer and said electro-optic material layer further
comprises a second optical interface layer which includes at least one
electrode, disposed in an orthogonal relation to the at least one
electrode of said first optical interface layer, for electrically
connecting a respective driving transistor of said processor layer to said
electro-optic material layer.
12. An image display apparatus including:
an array of very large scale integration (VLSI) semiconductor devices, each
of said plurality of VLSI semiconductor devices including:
a transparent cover layer;
a second layer having electrodes thereon;
a layer of electro-optic material disposed between said transparent cover
layer and said second layer;
a processor layer which includes drive electronics for creating driving
signals which are applied to said electro-optic layer, and processing
electronics, responsive to a series of two dimensional projections of an
object and to wavefront interference information which is independent of
the object data in the series of two dimensional projections of said
object, for combining the two dimensional projections and the wavefront
interference information once the series of two dimensional projections is
provided thereto, said drive electronics responsive to said processing
electronics for creating driving signals which create a diffraction
grating in said electro-optic layer to thereby provide a holographic image
of an object from a number of positions relative to said electro-optic
material layer;
wherein said electrodes of each of said VLSI devices supply signals to said
electro-optic material thereof such that each of said electrodes has a
corresponding through hole in the second layer and each of said electrodes
faces outwardly towards a viewer of the device.
13. An apparatus according to claim 12, wherein the diffraction grating
created in said electro-optic material of each of said VLSI devices
include interference patterns which generate a holographic image.
14. An apparatus according to claim 12, wherein the electrodes contacting
the electro-optic material of each of said VLSI devices are arranged in a
plane which is parallel to a plane of said transparent cover layer wherein
two of said electrodes apply an electric field through the electro-optic
material, said electric field beginning at one of said two electrodes and
ending at the other of said two electrodes.
15. An apparatus according to claim 12, wherein the processing layer of
each of said VLSI devices provides said signals to the electrodes such
that said display provides both horizontal and vertical parallax.
16. An apparatus according to claim 12, wherein the drive electronics of
each of said VLSI devices include a plurality of shift registers and a
plurality of drive transistors, and wherein said shift registers store
image information and provide signals to the drive transistors for
supplying voltages to said electro-optic material layer.
17. A device for rendering a holographic image, comprising:
a display device;
means for producing a series of two dimensional projections of an object to
be rendered for a plane which is coincident with a plane of the display
device;
means for producing wavefront interference information, independent of the
object data in the series of two dimensional projections of an object,
relative to an intermediate plane located at a predetermined position
relative to the display device;
means, connected to the means for producing two dimensional projections,
the means for producing wavefront interference information, and the
display device, for combining said two dimensional projections and said
wavefront interference information once the series of two dimensional
projections of an object has been produced; and
means, connected to the display device and the means for combining said two
dimensional projections and said wavefront interference information, for
creating a diffraction grating in said display device based upon a
combination of the two dimensional projections and the wavefront
interference information to thereby provide a holographic image of an
object from a number of positions relative to said display device;
wherein said means for creating a diffraction grating includes:
means for generating an electrical signal based upon a combination of the
two dimensional projections and the wavefront interference information;
means for applying the generated electrical signal to a drive transistor
located in a first layer of a multilayer display module;
means for producing a drive signal by said drive transistor in response to
the generated electrical signal;
means for transmitting said drive signal through at least a second layer of
said multilayer display module to a third layer of said multilayer display
module which is an electrical contact layer;
means for transmitting said drive signal from said third layer to an
electrode connected to a fourth layer which is an electro-optic layer; and
means for creating the diffraction grating in said electro-optic layer in
response to said drive signal transmitted from said fourth layer. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to display systems which are capable of providing
three-dimensional images. More particularly, the present invention
provides a holographic display system which can display three-dimensional
images. In particular, the display system can provide different
perspective images for different vantage points simultaneously. Simpler
versions can provide monochromatic images, however in more sophisticated
versions color images may also be provided.
Discussion of Background
Three-dimensional display systems are increasingly in demand for a wide
variety of applications. Dimensional imaging can be advantageously
utilized in medical, military and entertainment fields. In general, the
image to be displayed can be provided by a camera or generated by
computer. An image to be displayed may also be generated by a combination
of the two, such as where an image provided by a camera is combined with a
superposed image, such as a grid which indicates the size or location of
the camera generated image. The image could also be based upon ultrasound,
magnetic resonance, or other types of sensing/recording instruments.
Whether the images are provided by a camera or other instrument, the image
can also be modified or enhanced by a computer.
When a human observes an object, the object is observed as
three-dimensional (including height, width and depth), with the depth
perception resulting from the simultaneous observation of the object from
two different observation points corresponding to each of the observer's
two eyes. In a display system, often a three-dimensional image is
represented by a two-dimensional projection, or in other words, the depth
of the object is merely represented as a projection extending from a top
or side of the object and may, for example, be tapered somewhat to give
the appearance of depth. However, such a two-dimensional projection is not
a true three-dimensional image, since the same image would be observed by
each eye. In a typical three-dimensional movie, a stereo view is provided
which is more nearly three-dimensional than a two-dimensional projection
since a different image is provided for each of the observer's eyes.
However, such a view is stereoscopic, not truly three-dimensional because
observers at different vantage points in the theater see the same image,
and the image is truly correct only for the viewer located in the position
for which the stereo image was created. In addition, special glasses are
also necessary to view the three-dimensional image.
An early form of three-dimensional imaging, referred to as a Wheatstone
stereoscope, is shown in FIG. 1. In this arrangement, the observer is
provided with a dimensional image as a result of the simultaneous
observation of two different images, with a different image provided for
each eye. In viewing the images, the observer would look into a viewing
device in which the right eye would observe a first picture 1, typically
via a mirror 1a, while the left eye observes a second picture 2 via mirror
2a. The resultant image appears three-dimensional to the observer since
the respective pictures 1, 2 are of the same subject matter, however they
are taken from two different vantage points. More particularly, the first
picture would be formed by a camera obtaining an image of a given subject
matter, with the second image formed by a camera recording the same
subject matter, however with the vantage point for the second camera
spaced from the vantage point of the first camera by a specified distance
(typically about 65 mm, which is an average inter-ocular spacing between a
viewer's eyes). The images can be recorded substantially simultaneously by
a camera having two lenses which are spaced by the inter-ocular
separation, or may be formed by a single camera mounted upon a slide bar
or rail such that an image is formed at one vantage point, and the camera
is moved by the inter-ocular separation to a second vantage point at which
the second image is formed. By virtue of the simultaneous observation of
two different images of the same subject matter, a three-dimensional
appearance is provided to the viewer. However, the image is not truly a
three-dimensional representation of the subject matter, since the image
lacks motion parallax. In other words, the reproduced image does not
change when the observer of the reproduced image changes their vantage
point or viewing direction.
FIG. 2 shows a second form of stereoscopic display referred to as a
lenticular display. This type of display was often found in Cracker-Jack
boxes in the 1950's. In this arrangement, a lenticular lens sheet 10 is
provided which includes a set of cylindrical lenses 10a. A picture 12 is
provided which has been taken by a camera while moving, with the picture
taken through the same lenticular lens utilized during playback or
viewing. For a particular vantage point of the observer, a stereo pair is
respectively played back respectively to each of the left and right eyes
(i.e. one view for each eye), with the viewer only seeing a view recorded
by the camera for a particular instant. Thus, as the viewer moves
horizontally in viewing the image (the up and down direction in FIG. 2),
the viewer will observe different stereo pairs successively corresponding
to different instances recorded by the camera. A lenticular display thus
contains three-dimensional information and is an improvement over the
Wheatstone stereograph in that it provides motion parallax or horizontal
parallax (i.e., different images as the observer moves horizontally with
respect to the display). However, the lenticular display does not provide
vertical parallax and thus cannot itself provide for a complete full
parallax three-dimensional image.
In a fly's eye display , both vertical and horizontal parallax are provided
as the image is recorded and played back through a rectangular array of
fly's eye lenses. More particularly, as shown in FIG. 3A, an image of an
object is recorded on a photographic plate 16 through the fly's eye lens
14 while the camera is moving. The fly's eye lens 14 is a rectangular
array of lenses (each resembling a section of a sphere) such that, in
addition to the plurality of lenses shown vertically in FIG. 3A, the array
also extends horizontally (or into the page as shown in FIG. 3A). During
playback, the photographic plate is illuminated from behind and, for a
particular viewer position, the viewer will only see the view or image
seen by the camera at that particular instant or point. Thus, the viewer
sees a stereo pair which is different at different vantage points, such
that both horizontal and vertical parallax is provided. Even though both
horizontal and vertical parallax are provided, the fly's eye approach has
the shortcoming in that it is difficult to produce or simulate
electronically, since the display must be able to display both horizontal
and vertical parallax information simultaneously.
Other types of three-dimensional simulations can include shutter goggle
displays in which the user wears glasses containing polarizing screens or
shutters, with the shutter for the left eye acting as a barrier for images
intended for the right eye and vice versa. An extension of the shutter
goggle technique is the provision of a head mounted display in which a
small television monitor is provided for each eye, with head position
sensing devices provided on the helmet such that the image provided to
each eye varies as the position of the head varies. Such systems are
utilized today in virtual reality systems which are becoming particularly
popular in arcades.
Another approach to forming dimensional images involves formation of a
hologram. Forming a holographic display typically involves forming an
image on a holographic plate by dividing a single laser beam into two
components, one of which falls directly upon the holographic plate while
the other is reflected from the object and then onto the holographic
plate. Referring to FIG. 4, in recording a hologram, a coherent source of
light such as laser 20 provides a light beam which is first reflected by a
mirror 22 and then a beam splitter 24 splits the beam into first and
second component beams represented at 26, 28. The first beam 26 is then
reflected by another mirror 30 and then impinges directly upon the
holographic plate 32. The second beam 28 is directed toward the object 36
via mirror 34, and the beam is diffusely reflected (represented by
wavefronts 38) and impinges upon the holographic plate 32. As would be
understood by one skilled in the art, spatial filters F are also provided
for "cleaning" the light source and controlling the size of the beam since
it progressively enlarges or propagates as it leaves the filter. The
object beam and reference beam thus interfere with one another within the
holographic plate and form an interference pattern which accurately
documents the wavefronts present during the recording process.
FIG. 5 illustrates an arrangement for viewing or reconstructing the image
formed on the holographic plate 32. More particularly, a laser 20 provides
a beam via mirrors 40, 42, 44 which then illuminates the holographic plate
32 such that the observer 46 sees a reconstructed virtual image 48. The
holographic plate 32 has recorded the interference pattern (i.e., as
formed in FIG. 4) as a variation in the intensity of the plate's density,
and thus can be illuminated and viewed by a monochromatic light source
provided by the laser 20 which is then viewed by the observer 46 on the
opposite side of the holographic plate 32.
If the reconstruction light source is not monochromatic, for example if a
white light is utilized, a "smeared out" reconstructed image is formed as
shown in FIG. 6. For each wavelength of light in the reconstruction beam,
a different image is reconstructed, with three images shown in FIG. 6
corresponding to red, green and blue reconstructed images 50, 52, 54
resulting from the white light source 56. The observer 46 sees the
different images as appearing at different locations, and include
rotation, size and distance aberrations which are related to the
wavelength difference between the recording light source and the
respective wavelengths of the reconstruction beam.
FIG. 7 illustrates an arrangement for forming white light viewable
holograms, which are typically found on credit cards. Initially, a master
hologram is formed on a holographic plate 32 in the manner described
earlier. The holographic plate 32 is then illuminated by a beam identical
to its original reference beam provided by laser 20. The laser 20 also
provides a reference beam to a second holographic plate 33. Thus, the
laser 20 provides a reconstruction beam via mirrors 60, 62, 64 and beam
splitter 61 such that the reconstructed real image of holographic plate 32
is illuminated and falls upon the second holographic plate 33. The laser
20 simultaneously provides a reference beam via mirror 60 and beam
splitter 61 thereby providing a reference beam to the second holographic
plate 33 such that a second hologram is formed. The image formed 35
appears to straddle the holographic plate 33 and, when viewed by a
monochromatic light source, the image appears to be surrounding the plate
33. For objects having little depth, white light illumination results in a
slightly fuzzy pastel holographic image.
In a rainbow hologram (a type of white light viewable hologram), a transfer
is made from an original hologram to a second holographic plate as shown
in FIG. 7, however only a slit of the original hologram (32) is allowed to
illuminate the second holographic plate 33. Confinement of the
illumination to a slit is achieved either by utilizing a slit beam
produced by a cylindrical lens, or by masking the first holographic plate
32. As a result, illumination of the second holographic plate 33 not only
reconstructs the image formed on the plate 33, but also reconstructs the
slit in space. As shown in FIG. 8, when this type of hologram is
reconstructed using white light 56' to illuminate the second holographic
plate H2, a plurality of reconstructed images are formed, for example as
shown at 65, 66, 67, corresponding to red, green and blue reconstructed
images. Each of the reconstructed images will have the slit S therein such
that the viewer must view the recorded object from an angle/position in
which all three of the slits are aligned. If viewed from a position in
which the slits are not aligned, the object image will not be visible.
Thus, the rainbow hologram approach overcomes the diffusion or "smearing
out problem" (FIG. 6) by providing a slit which requires the viewer to be
at the properly aligned position to view the object image. Since the image
is lost if the vertical relationship between the viewer and the
holographic plate changes, this approach does not provide vertical
parallax. However, the vertical parallax is traded for the ability to view
the hologram by white light using the slit.
FIG. 9 illustrates another method in which a white light visible hologram
is produced. As shown in FIG. 9, a first hologram or master hologram 75
(e.g. corresponding to the first hologram 32 of FIG. 7) is transferred
onto a second holographic plate 77 as it is illuminated by the
reconstruction beam emanating from laser 20 and passing through mirror 74,
beam splitter 76 and mirror 78. However, the reference beam for the
secondary hologram 77 falls on the opposite side of the holographic plate
77 via mirrors 70, 72 (in contrast to the FIG. 7 arrangement in which the
reference beam and the image from the first holographic plate are directed
upon the same side of the holographic plate). As a result, an interference
filter is created in the secondary holographic plate 77, with the plate 77
also having a diffraction pattern which characterizes the object. Thus,
the holographic recording also includes a monochromatizing interference
filter, and the image is reconstructed by Bragg diffraction. A hologram
which is formed in the method shown in FIG. 9 can be illuminated by white
light and the internal interference filter filters out all but one
wavelength (or a narrow band of wavelengths) which is used to reconstruct
the image for the observer. The reflection transfer hologram thus produces
images which are monochromatic, however the image maintains vertical
parallax.
The foregoing various types of holograms have a severe shortcoming in that
the object must be small, still, and insensitive to vibration. Thus,
holograms of live and moving objects are difficult to produce. In
addition, the object must be a real object from which the hologram is
produced, and simulated images or data cannot be formed into a hologram
utilizing the real-object technique. To overcome these shortcomings, a
holographic stereogram technique has been developed as shown for example
in FIG. 10. In this arrangement, a series of stereo pairs are recorded on
35 mm film. Subsequently, the film 80 (having a series of stereo pairs
thereon) is recorded frame by frame on the holographic plate utilizing the
reference beam 82 and the image beam 84 passing through the film 80, lens
86, diffusing screen 88 and then onto the holographic plate 90. A series
of the small strip holograms are produced on the master 90 each having the
height of the plate, but only 3 mm wide as indicated by the slit S. Each
strip hologram is a different view of the diffusion screen, with each
exposure corresponding to a different frame of the 35 mm motion picture
film which is projected onto the diffusion screen. The individual strips S
are 3 mm which corresponds to approximately one pupil diameter, and each
pair of strips which are 65 mm apart (inter-ocular spacing) constitute a
stereo pair visible for a particular vantage point of the viewer. The
holograms formed on plate 90 are then transferred to a second hologram or
viewable hologram (not shown) in the manner shown in FIG. 9.
In viewing the viewable hologram of the FIG. 10 arrangement, the observer
is looking into the reconstructed slits of the hologram 90, with each
individual slit having the image projected on the diffusion screen (i.e.
from the film) when that particular slit was recorded. The two slits 65 mm
apart (corresponding to inter-ocular or inter-pupil spacing) each carry
the respective left/right image of a stereo pair, and thus the observer
sees a free-viewing stereo image. A very high frequency (10.sup.3 lp/mm or
line parts/mm) holographic grating is generated by the holographic
stereogram arrangement of FIG. 10, with the holographic grating only
utilized as a beam steering mechanism for a relatively low frequency (1
pixel/mm) photographic image. The sequence of stereo pairs may be produced
by a number of methods, for example by a stereoscopic motion picture
camera or by rotating an object (recorded by a standard camera lens or
even under an electron microscope) or by computer simulation of
three-dimensional models.
Referring now to FIG. 11, a multiplex hologram is shown which, like the
holographic stereogram arrangement of FIG. 10, can utilize photographic
film footage for recording the holographic images. However, instead of
recording a set of slit holograms taken from a diffusion screen as shown
in FIG. 10, in the multiplex hologram arrangement, each slit hologram
recording is a single photographic frame recorded through a cylindrical
lens. Thus, each frame of the film 91 (FIG. 11) includes an image recorded
through a cylindrical lens with each frame forming a slit hologram on the
plate 92 as the image beam 94 passes through the film 91, lens 98 and onto
the holographic plate 92, while the reference beam 96 simultaneously falls
upon the plate 92. As a result, a display is formed which is similar to
the lenticular display discussed earlier, with the holographic display
similar to a sequence of cylindrical lens images (with the lenses of FIG.
11 extending orthogonally as compared with the FIG. 2 arrangement).
The foregoing arrangements are based upon the use of amplitude holograms
or, in other words, the final fringe patterns are set up as variations in
the amount of opaque silver in the film or holographic plate. As a result,
most of the incident reconstruction beam is attenuated by the silver film
and the diffraction efficiency of the hologram is on the order of a few
percent. Typically, most holographic systems utilize phase variation. In
the photographic domain, the holographic plate is first processed in
normal silver chemistry. The final pattern includes the distribution of
silver/no silver regions, with the silver sites re-halogenated to silver
halide.
The result is a phase hologram in which the entire holographic effect is
obtained by refraction of light and the chang | | |
