ICIC Express Letters ICIC International ⓒ2010 ISSN 1881-803X
Volume 4, Number 5, October 2010
pp. 1–6
Novel View for Fractional Fourier Transform and the Applications on Optical Image
Encryption
Lin-Lin Tang
1
, Jeng-Shyang Pan
2
1,2
School of Computer Science and Technology,
Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, China
Received Dec. 2012; accepted Feb. 2013
A
BSTRACT. A novel view for the FRactional Fourier Transform (FRFT) and its
applications on the optical image encryption is proposed in this paper. Sampling method
is applied onto the kernel function of the fractional Fourier transform to analyze the
diversity of the operator. Related applications based on multiplicity about optical image
encryption are introduced. Good performance in the experiment shows its efficiency.
Keywords: Fractional Fourier Transform, Kernel Function, Encryption
1. Introduction. As we all know, the Fourier transform is well known as providing
technique for solving scientific problems. It plays an important role in the theory of many
branches of science such as general science and engineering [1, 2]. Especially, after 1940,
with the advent of computer technology and quick development of computer science, fast
Fourier transform (FFT) penetrated almost all the domains of modern science and
technology. And the commonly used discrete Fourier transform definition (DFT) is shown
as below.
2
1
0
ˆˆ
,0,,1
k
N
ikn
iw
N
n
xk xe xne k N
(1)
Here,
,0,,1xn n N
is a discrete signal and the
2
k
wk
N
.
The research history about the fractional Fourier transform: In 1937, E. U. Condon [3]
firstly set the foundation of fractional Fourier transform by using the method of continuous
group in thesis Immersion of the Fourier Transform in a Continuous Group of Functional
Transformation. And then, V. Bargmann [4] used Fourier transform as a special integral
transform to study Hilbert space of analytic functions. In 1980, based on the eigenvalues
and eigenfunctions of Fourier transform, V. Namias [5] proposed Fourier transform with
fractional order in his thesis. Later that year, A. C. McBride and F. H. Kerr [6] discussed
precisely the definition proposed by V. Namias in form of integral transform. From 1993,
fractional Fourier transforms are applied as new tools in signal information process and
optical fields. One of the most famous applications for this new operator is the optical
image encryption technique which is firstly proposed by Tao in 2008 [7] by using the
multi-parameter property to apply the transform onto the image. Though, there have been
many applications on digital watermarking based on FRFT [8, 9], we pay attention to
encryption applications here.
Some related basic theory is introduced in section 2, the sampling view for kernel
function method to analyze the multiplicity of the operator is proposed in section 3. Some
idea and experiments for the encryption methods are given in section 4. A conclusion is