Holomonitor™
Special Report:
Progress Toward 3D Holographic
Animation
This issue of Holomonitor™ is a special
report on progress toward holographic animation. A hologram
is an image that is created by two or more overlapping beams of coherent
light. In coherent light, the peaks and valleys of the light
waves are aligned. This differs from conventional light in which
the peaks and valleys of the light waves are random relative to each other.
Lasers are a common form of coherent light. In a hologram, the combination
of wave peaks and valleys from the two or more intersecting beams of light
cause an interference pattern that creates an image.
Holographic animation may be defined as
a moving three-dimensional image that meets the following three criteria:
(1) holographic technology -- the image is an interference pattern
from two or more beams of light; (2) three-dimensional perspective
-- the three-dimensional perspective of the image changes in a relatively-continuous
manner as a viewer moves and the angle from which they view the hologram
changes; (3) independently moving content -- the content of
the image changes, over a relatively-significant duration of time, independently
of changes in viewer location. Holographic animation differs
from conventional holograms. Conventional holograms can provide
a limited number of different images that change with changes in viewer
position, but conventional holograms do not provide a sufficient number
of images to create a changing image over a significant duration of time
and the content of the images does not change without changes in viewer
position.
Holographic animation has been a popular
theme in science fiction, such as the Star Wars movies, for many years.
Technophiles have been enthusiastic that holographic animation may be "right
around the corner" for many years. Reality, however, has disappointed.
For many technophiles, optimism concerning progress toward holographic
animation has turned into skepticism. However, during the last five
years there have been several research breakthroughs that may finally be
laying the foundation for true holographic animation. This report
provides a summary of this progress toward holographic animation.
Before discussing real breakthroughs toward
holographic animation, we need to clear the air concerning recent use of
the term "holographic" when referring to some display techniques that are
not really holographic at all. Technically, the term holographic
only refers to images created from interference patterns of coherent light. |
However, the label
"holographic" has been used in the media as a label for many display techniques
with three-dimensional or quasi-three-dimensional qualities, regardless
of whether any holographic technology is used.
For example, the term "holographic" has
been used when a 2D image is projected onto a tilted semi-transparent surface
to create the illusion of an object "floating in space." However,
this technique does not involve holography. In fact, it is an old
illusion know as "Pepper's Ghost" that predates the discovery holography
by many decades. As another example, the term "holographic" was used
during coverage of the 2008 election when CNN featured a "three-dimensional"
illusion of reporter Jessica Yellin being "beamed into" the newsroom.
However, her image was not a hologram. Other image display techniques
that are called "holographic," but do not involve holography, include:
projecting a non-coherent light image onto a moving (e.g. spinning) surface;
or using a moving (e.g. spinning) light-emitting surface to create a three-dimensional
image. Although these are useful approaches to 3D imaging, they are
not holographic animation according to three-point definition above and
are not reviewed in this issue of Holomonitor™.
Given the high expectations concerning
holographic animation that have been repeatedly met with disappointment
during recent decades, it is risky to say that holographic animation is
now "just around the corner." However, it is safe to say that there has
been significant progress that has brought it closer to reality than ever
before. In this issue of Holomonitor™, we summarize progress toward
true holographic animation at three key research locations:
1. Drs. Stephen Benton, V. Michael Bove,
and Quinn Smithwick at the Massachusetts Institute of Technology (MIT)
Drs. Benton, Bove, and Smithwick at MIT
have pioneered true holographic animation with a progressive series of
holographic video display systems (called the "Mark I", "Mark II", and
"Mark III") over the past two decades. This work was started
by Dr. Benton, who passed away, and is now led by Drs. Bove and Smithwick.
These holographic video display systems use Acousto-Optic Modulators (AOMs)
to create computer-generated moving holograms. The AOM converts a
computer-generated video signal into vibrations of a structure which, in
turn, modifies the brightness and frequency of laser light that passes
through that structure. The modified laser light is then distributed
vertically and horizontally across a translucent surface (called a diffuser)
by a set of moving mirrors.
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As the beams intersect in the translucent
surface, they create a moving three-dimensional image. Images from these
holographic video display systems are still relatively small and low resolution,
but are improving. The Mark I created 25x25x25 mm images, around
20 frames per second, with a 15-degree view zone. The Mark II created
150x75x150 mm images, around 2.5 frames per second, with a 30-degree view
zone. The Mark III creates 80x60x80 mm images, around 30 frames per
second, with a 24-degree view zone. Work on the Mark III includes
efforts to make holographic animation possible with common hardware, such
as a PC video card, instead of expensive customized equipment.
2. Drs. Harold Garner, Bala Munjuluri,
and Michael Huebschman at the University of Texas Southwestern Medical
Center (UTSMC)
Drs. Garner, Munjuluri, and Huebschman
at UTSMC have pioneered holographic animation using Digital Micromirror
Devices (DMDs). DMDs are arrays of hundreds of thousands of miniature
mirrors,
each of which can be moved thousands of times per second by a computer.
Dr. Garner and colleagues use DMDs to modify the phase of laser light beams.
As these modified light beams intersect in a volume of display material,
they create a moving three-dimensional image. The volume of
display material can be a translucent gel. Alternatively, the volume
of display material can be a series of thin liquid crystal panels whose
transparency can be changed electronically. For example, all the
panels except one can be made transparent at a given instant and which
panel is non-transparent is changed sequentially. If this sequential
change is sufficiently fast, then the eye compiles images on the sequential
panels into a single three-dimensional image. Prototype display systems
at Texas have created 30x28x2.5 cm images, at around 60 images per second,
with a very wide view zone. They are working on more advanced systems.
3. Drs. Nasser Peyghambarian and Savas
Tay at the University of Arizona (UA)
Drs. Peyghambarian and Tay at UA achieved
a break-through in holographic animation by creating a holographic display
system in which holograms can be sequentially erased and written.
They achieved this using a two-part media system that writes and erases
image data via electric fields. One part is a photorefractive
polymer that creates small electric fields. The other part is a dye
that changes in response to the electric fields. The combined result
of these two parts is a dynamic holographic recording material that allows
updating of images. Their current prototype creates 4x4 inch images,
in only one color, with a refresh rate of a few minutes. They are
working on a larger 1-square-foot version with quicker refresh rates. |
