Decemb er 10, 2009 / Vol. 7, No. 12 / CHINESE OPTICS LETTERS 1083
Computational approaches for fast generation
of digital 3D video holograms
Invited Paper
Seung-Cheol Kim and Eun-Soo Kim
∗
3D Display Research Center, Department of Electronic Engineering, Kwangwoon University,
Wolgye-Dong, Nowon-Gu, Seoul 139-701, Korea
∗
E-mail: eskim@kw.ac.kr
Received July 17, 2009
Several approaches for fast generation of digital holograms of a three-dimensional (3D) object have been
discussed. Among them, the novel look-up table (N-LUT) method is analyzed to dramatically reduce the
numb er of pre-calculated fringe patterns required for computation of digital holograms of a 3D object
by employing a new concept of principal fringe patterns, so that problems of computational complexity
and huge memory size of the conventional ray-tracing and look-up table methods have been considerably
alleviated. Meanwhile, as the 3D video images have a lot of temporally or spatially redundant data in
their inter- and intra-frames, computation time of the 3D video holograms could be also reduced just by
removing these redundant data. Thus, a couple of computational methods for generation of 3D video
holograms by combined use of the N-LUT method and data compression algorithms are also presented
and discussed. Some experimental results finally reveal that by using this approach a great reduction of
computation time of 3D video holograms could be achieved.
OCIS codes: 090.1760, 090.5694, 050.1940, 999.9999 (look-up table).
doi: 10.3788/COL20090712.1083.
1 Introduction
Recently, a lot of research works have been actively done
on the three-dimensional (3D) imaging and display tech-
nology due to its high interests throughout the world
[1−7]
.
Among them, the holographic technology has been par-
ticularly regarded as one of the promising and attractive
approaches for creating the most authentic illusion of ob-
serving volumetric objects. It is because the holographic
technology can supply very high-quality object images
and accurate depth cues viewed by human eyes without
any special observation devices
[8−11]
.
However, recording holograms of real 3D objects in the
optical holographic system may demand wave interfer-
ence between the two intense laser beams with a high de-
gree of coherence between them in a dark room. There-
fore, this system must be kept to be very stable since
even a very slight movement can destroy the interference
fringes, in which both intensity and phase information
of the 3D objects are contained. These requirements, to-
gether with the development and printing processes, have
prevented conventional hologram recorders from becom-
ing widely used in the outdoor recording.
As a partial solution for these limitations of the
conventional holographic system, a new approach, so-
called computer-generated hologram (CGH), has been
suggested
[12]
. A CGH is a digital hologram generated
by computing the interference pattern produced by the
object and the reference waves. Using this CGH pat-
tern, an electro-holographic 3D display system can be
constructed
[13]
.
In this approach, a ray-tracing method has been orig-
inally employed for calculating the contributions at the
hologram plane from each object point source. That is,
an object image to b e generated can be approximated as
a collection of self-luminous points of light, therefore the
fringe patterns for all object points are calculated with
the ray-tracing method and added up to obtain the whole
interference pattern of the object image.
This method can produce arbitrary 3D images includ-
ing image-plane holograms, in which images might lie in
the vicinity of the hologram, so that it might be more
suitable for various display geometries. However, this
approach shows a computation complexity, since it re-
quires one by one calculation of the fringe pattern per
image point per hologram sample. Thus, real-time gen-
eration of the CGH pattern for a 3D image could not be
achievable
[14]
.
To overcome this problem, a look-up table (LUT)
method has b een presented by Lucente
[14]
. In this
method, an object image to be generated is also ap-
proximated as a collection of self-luminous points of
light likewise the case of the ray-tracing method, but all
fringe patterns corresponding to point source contribu-
tions from each of the possible locations in image volume
are pre-calculated and stored in the LUT. Then, in the
process of CGH generation, fringe patterns for each point
in the object image can be generated just by accessing the
corresponding ones from the pre-calculated LUT, which
is contrary to the ray-tracing method, where fringe pat-
terns for all object points are directly calculated on the
one by one basis. Therefore, a great increase in computa-
tion speed can be obtained with this LUT method. But
the greatest drawback of this approach is the enormous
memory size of the LUT
[15]
.
Recently, a novel look-up table (N-LUT) method to be
able to significantly reduce the number of pre-calculated
interference patterns required for generation of digital
holograms has been proposed
[15]
. In this N-LUT method,
1671-7694/2009/121083-09
c
° 2009 Chinese Optics Letters