Decemb er 10, 2009 / Vol. 7, No. 12 / CHINESE OPTICS LETTERS 1
Fresnel incoherent correlation hologram-a review
Invited Paper
Joseph Rosen, Barak Katz
1
, and Gary Brooker
2∗∗
1
Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev,
P.O. Box 653, Beer-Sheva 84105, Israel
2
Johns Hopkins University Microscopy Center, Montgomery County Campus, Advanced Technology Laboratory,
Whiting School of Engineering, 9605 Medical Center Drive Suite 240,
Ro ckville, MD 20850, USA
∗
E-mail: rosen@ee.bgu.ac.il;
∗∗
e-mail: gbro oker@jhu.edu
Received July 17, 2009
Holographic imaging offers a reliable and fast method to capture the complete three-dimensional (3D)
information of the scene from a single p erspective. We review our recently proposed single-channel optical
system for generating digital Fresnel holograms of 3D real-existing objects illuminated by incoherent light.
In this motionless holographic technique, light is reflected, or emitted from a 3D object, propagates through
a spatial light modulator (SLM), and is recorded by a digital camera. The SLM is used as a b eam-
splitter of the single-channel incoherent interferometer, such that each spherical beam originated from
each object point is split into two spherical beams with two different curve radii. Incoherent sum of
the entire interferences between all the couples of spherical beams creates the Fresnel hologram of the
observed 3D object. When this hologram is reconstructed in the computer, the 3D properties of the object
are revealed.
OCIS codes: 100.6640, 210.4770, 180.1790.
doi: 10.3788/COL20090712.0000.
1. Introduction
Holography is an attractive imaging technique as it
offers the ability to view a complete three-dimensional
(3D) volume from one image. However, holography is
not widely applied to the regime of white-light imaging,
because white-light is incoherent and creating holograms
requires a coherent interferometer system. In this review,
we describe our recently invented method of acquiring
incoherent digital holograms. The term incoherent digi-
tal hologram means that incoherent light beams reflected
or emitted from real-existing objects interfere with each
other. The resulting interferogram is recorded by a dig-
ital camera and digitally processed to yield a hologram.
This hologram is reconstructed in the computer so that
3D images appear on the computer screen.
The oldest methods of recording incoherent holograms
have made use of the property that every incoherent ob-
ject is composed of many source points, each of which
is self-spatial coherent and can create an interference
pattern with light coming from the p oint’s mirrored
image. Under this general principle, there are vari-
ous types of holograms
[1−8]
, including Fourier
[2,6]
and
Fresnel holograms
[3,4,8]
. The process of beam interfering
demands high levels of light intensity, extreme stability
of the optical setup, and a relatively narrow bandwidth
light source. More recently, three groups of researchers
have proposed computing holograms of 3D incoherently
illuminated objects from a set of images taken from differ-
ent points of view
[9−12]
. This method, although it shows
promising prospects, is relatively slow since it is based on
capturing tens of scene images from different view angles.
Another method is called scanning holography
[13−15]
, in
which a pattern of Fresnel zone plates (FZPs) scans the
object such that at each and every scanning position,
the light intensity is integrated by a point detector. The
overall process yields a Fresnel hologram obtained as a
correlation between the object and FZP patterns. How-
ever, the scanning process is relatively slow and is done
by mechanical movements. A similar correlation is ac-
tually also discussed in this review, however, unlike the
case of scanning holography, our proposed system carries
out a correlation without movement.
2. General properties of Fresnel
holograms
This review concentrates on the technique of incoher-
ent digital holography based on single-channel incoher-
ent interferometers, which we have been involved in their
development recently
[16−19]
. The type of hologram dis-
cussed here is the digital Fresnel hologram, which means
that a hologram of a single point has the form of the
well-known FZP. The axial location of the object point
is encoded by the Fresnel number of the FZP, which is
the technical term for the number of the FZP rings along
the given radius.
To understand the operation principle of any general
Fresnel hologram, let us look on the difference between
regular imaging and holographic systems. In classical
imaging, image formation of objects at different distances
from the lens results in a sharp image at the image plane
for objects at only one position from the lens, as shown
in Fig. 1(a). The other objects at different distances
from the lens are out of focus. A Fresnel holographic
system, on the other hand, as depicted in Fig. 1(b),
1671-7694/2009/120xxx-08
c
° 2009 Chinese Optics Letters