934 CHINESE OPTICS LETTERS / Vol. 7, No. 10 / October 10, 2009
Adaptive interference hyperspectral image compression
with spectrum distortion control
Jing Ma (
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)
∗
, Yunsong Li (
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), Chengke Wu (
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), and Dong Chen (
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)
State Key Laboratory of Integrated Service Networks, Xidian University, Xi’an 710071, China
∗
E-mail: jingma@mail.xidian.edu.cn
Received December 25, 2008
As one of th e next generation imaging sp ectrometers, interferential spectrometer has been paid much
attention. With traditional spectrum compression methods, the hyperspectral images generated by inter-
ferential spectrometer can only be protected with better visual quality in spatial domain, but its optical
applications in Fourier domain are often ignored. So the relation b etween the distortion in Fourier domain
and the compression in spatial domain is analyzed in this letter. Based on this analysis, a n ovel coding
scheme is proposed, which can compress data in spatial domain while red ucing the distortion in Fourier
domain. The bitstream of set partitioning in hierarchical trees (SPIHT) is truncated by adaptively lifting
the rate-distortion slopes of zerotrees according to the priorities of optical path difference (OPD) based
on rate-distortion optimization theory. Experimental results show that the proposed scheme can achieve
better performance in Fourier domain while maintaining the image quality in spatial domain.
OCIS codes: 100.4145, 100.2960, 070.4790.
doi: 10.3788/COL20090710.0934.
Interferential spectrometer is carried on the satellite for
the purp ose of space exploration, military reconnais-
sance, and weather forecast
[1]
. Because of its adva n-
tages of high throughput, multi-channel, and great reso-
lution, interferential spectrometer has be e n used on the
Chinese Chang’e Moon Exploration Satellite for the sub-
stance c lassification, resource investigation, and remote-
sensing. Its unique character is that its optical appli-
cations are mainly in Fourier domain, which is differ-
ent from the dispersive spectrometer data, such as air-
borne visible/infrared imaging spectrometer (AVIRIS).
Interference hyperspectral images should be compressed
immediately when formed on the charge coupled de-
vice (CCD) of interferential spe ctrometer o n the satel-
lite, which is in spatial domain. Futhermore, a complex
and non-real-time post-processing is adopted to recover
the spectrum on the ground in Fourier domain
[2]
. Gr eat
amount of data will be generated during the imaging on
interferential spectrometer. Thus, challenges are brought
and spectrum sho uld be well protected during the high-
ratio data compression.
Several lossless compres sion methods
[3,4]
have been
proposed for the interferential spectrometer data. How-
ever, los sy compression is more efficient for transmission
if spectrum distortion can be controlled in an acceptable
level for optical application. Although there are some
lossy compression methods
[5]
for dispersive spec trome-
ter, they do not fit the requirements of interferential
sp e ctrometer due to different optical imag ing principles.
Hence, some methods
[6−8]
are proposed for interferen-
tial hyperspectral image but they only focus on the vi-
sual information rather than the spectrum information.
Due to the impor tance in the application for spectrum
analyzer, spectrum distortion in Fourier domain should
be paid more attention. Therefore, lossy compression
method with spectrum distortion control for interference
hyperspectral imag e is crucia l for the interferential spec-
trometer’s further applications on satellites.
In this letter, the relation between the compression in
spatial domain and the distortion control in Fourier do-
main is analyzed. Based on the achieved conclusion, we
propose the weighted rate-dis tortion optimization for set
partitioning in hierarchical trees (WRDO-SPIHT) which
impo ses different priorities on various optical path dif-
ference (OP D) pixels with rate-distortio n optimization
truncation for bitstream allocation of SPIHT according
to the characteristics of interference hyper spectral images
in Fourier doma in. This method can not only improve
the compression performance of SPIHT in spatial domain
but a lso achieve the balance of bitstream allocation be-
tween spatial and spectral distortion.
The optical principle of interferential spectrometer is
that the light forms two slim targets on the fore-focal
planes and is separated into a pair of coherent lights in
the interferometer. The interferogram shown in Fig. 1(a)
is collected from CC D detector by the optic collecting
system. The data I(x) in the same row of interferogram
generated by interference of coherent lights is called the
interference curve as shown in Fig. 1(b) and can be ex-
pressed as
I(x) =
Z
ν
max
ν
min
B(ν)e
2πνx
dν, (1)
where B(ν) is the spec tral distribution of source, v
min
and v
max
are extremums of wave number, x represents
OPD in interference curve.
According to the theory of irradiance, radiation con-
sists of a series of waves with finite lengths. It means
that there is one waveform during the coherence time τ
c
.
When B (v) = 1, I (x) can be expressed as
I(x) =
r
2
π
sin ((x − x
0
) τ
c
/2)
x − x
0
= τ
c
r
1
2π
Sa
(x − x
0
)τ
c
2
. (2)
1671-7694/2009/100934-04
c
2009 Chinese Optics Letters
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