Optics Communications 403 (2017) 296–303
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Optics Communications
journal homepage: www.elsevier.com/locate/optcom
Fast diffraction calculation of cylindrical computer generated hologram
based on outside-in propagation model
Jun Wang
a
, Qiong-Hua Wang
a,
*, Yuhen Hu
b
a
School of Electronics and Information Engineering, Sichuan University, Chengdu 610065, China
b
Department of Electrical & Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
a r t i c l e i n f o
Keywords:
Diffraction theory
Computer generated hologram
Cylindrical CGH
Holographic display
a b s t r a c t
Cylindrical computer-generated hologram is a promising approach to realize a display with 360
◦
field of view.
However, conventional cylindrical hologram employs an inside-out propagation model and suffers from two
main drawbacks: limited object size and lack of effective reconstructed method. Previously, we proposed to fix
these problems using an outside-in propagation model with reversed propagation direction of the inside-out
model. We also derived corresponding diffraction calculation formula for the outside-in propagation model. In
this work, we investigate a non-constant obliquity factor in the outside-in propagation model, and show that
it is the projection of the unit complex amplitude in the propagation direction onto the outer normal of the
observation point. We then propose to apply fast Fourier transform to accelerate the convolution operation
needed for diffraction calculation. We conducted experiments on inverse diffraction and reconstruction of the
cylindrical objects. Very encouraging results demonstrate the validity of this proposed approach.
© 2017 Elsevier B.V. All rights reserved.
1. Introduction
Holography is a promising three-dimensional (3D) display technique
because it can record and reproduce wholistic 3D information such as a
motion parallax, a convergence, an occlusion, an accommodation, and
so on. Usually holograms are made on flat surfaces which limit the
viewing angles. This limitation can be alleviated if holograms are made
on cylindrical surfaces [1–3]. Beside a 3D display, a cylindrical geometry
is also preferred for 3D volumetric imaging, such as computed tomog-
raphy, magnetic resonance images, and integral-floating display [4].
A cylindrical computer generated hologram (CGH) can provide 360
◦
horizontal field of view (FoV) as opposed to the limited FoV offered by
the conventional planar CGH. Furthermore, the amount of data needed
in a curved hologram is smaller than that in a planar hologram for the
same range of FoV [5]. With the developments of curved display and
recording devices, a cylindrical CGH with a ‘‘look around property’’ has
attracted much attention recently.
Sakamoto et al. [6] proposed a fast calculation method for the cylin-
drical hologram of a planar object using the angular spectrum of plane
wave and the fast Fourier transform (FFT) algorithm which exploits
the rotational shift invariance property between a planar surface and
a cylindrical surface. Continue on this work, Kashiwagi and Sakamoto
generated a cylindrical hologram of 3D object by slicing it into planar
*
Corresponding author.
E-mail address: qhwang@scu.edu.cn (Q.-H. Wang).
segments [7]. Sando et al. [8] demonstrated the propagation from
cylindrical surface as cylindrical waves by defining wave propagation in
cylindrical coordinates. By choosing the object also to be a concentric
cylindrical surface with the hologram, the shift invariance was pre-
served, and the FFT algorithm is applicable. Jackin et al. [9] define wave
propagation in the spectral domain in cylindrical coordinates, hence one
fewer FFT operation is needed. By applying this approach, they reported
successful reconstruction of a simple 3D object [10]. For a complex 3D
object, an algorithm of wavefront recording surface for fast calculation
of cylindrical CGH was proposed by Kim et al. [11]. Different from the
previous approaches, Yamaguchi et al. [12] generated the cylindrical
holograms by segmenting the cylindrical surface into elemental plane
surfaces. They also developed a computer generated cylindrical rainbow
hologram using the same method [13]. Above mentioned methods
consider wave propagation from the inner object surface to the outer
cylindrical observation surface using an inside-out propagation (IOP)
model. Due to the limited observation or hologram surface area, the
size of object may be limited. Moreover, the IOP model also needs to
calculate the diffraction distribution, which is propagated from outside
to inside cylindrical surface, during the reconstruction process.
Previously, by placing the object surface on the outer cylinder and
observation surface on the inner cylinder, we proposed an outside-
in propagation (OIP) model [14] with opposite propagation direction
http://dx.doi.org/10.1016/j.optcom.2017.07.045
Received 8 June 2017; Received in revised form 15 July 2017; Accepted 16 July 2017
Available online 2 August 2017
0030-4018/© 2017 Elsevier B.V. All rights reserved.