Method for enhancing visibility of hazy images based
on polarimetric imaging
Jian Liang,
1,2
Liyong Ren,
1,
* Enshi Qu,
1
Bingliang Hu,
1
and Yingli Wang
1
1
State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics,
Chinese Academy of Sciences, Xi’an 710119, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
*Corresponding author: renliy@opt.ac.cn
Received December 18, 2013; revised January 17, 2014; accepted January 20, 2014;
posted January 22, 2014 (Doc. ID 203159); published February 5, 2014
A novel polarimetric dehazing method is proposed based on three linear polarization images (0°, 45°, and 90°). The
polarization orientation angle of the light scattered by the haze particles is introduced in the algorithm. No addi-
tional image-processing algorithm is needed in the postprocessing. It is found that the dehazed image suffers from
little noise and the details of the objects close to the observer can be preserved well. In addition, this algorithm is
also proved to be useful for preserving image colors. Experimental results demonstrate that such an algorithm has
some universality in handling all kinds of haze. We think that this robust algorithm might be very suitable for
real-time dehazing. © 2014 Chinese Laser Press
OCIS codes: (100.2980) Image enhancement; (110.5405) Polarimetric imaging; (290.1310) Atmospheric
scattering.
http://dx.doi.org/10.1364/PRJ.2.000038
1. INTRODUCTION
Over the past decades, there has been great interest in polari-
metric imaging since it has been widely used in many imaging
applications [
1–3]. Several kinds of polarimetric cameras have
been proposed to satisfy different usages, such as wideband
cameras [
2], 3-Stokes parameters imaging cameras [4 ,5], and
underwater cameras [
6]. Moreover, polarimetric cameras that
can simultaneously obtain full-Stokes parameters are under
study by the techniques of liquid crystals [
7], plasmonic lenses
[
8], and Wollaston prisms [9].
Nowadays, hazy weather appears more and more fre-
quently as a result of pollution, and we all know that the vis-
ibility of an image taken directly in the haze is usually very
poor. This may cause some inconvenience in daily life. To
solve this problem, polarimetric imaging has been found to
be a useful method for effectively improving the visibility
of the image. In 2001, Schechner et al. [
10] first demonstrated
that one can enhance the quality of images taken in poor vis-
ibility weather by using polarimetric imaging. The basic prin-
ciple includes two aspects. The first one is to estimate the
intensity of the air light (scattered by the haze particles) ac-
cording to its partial-polarized property; the second one is to
remove the above-estimated part from the hazy image and
thus to obtain the visibility-enhanced image. In following
years, his group made much effort to discuss and perfect this
theory [
11–13]. Especially in 2009, they accomplished the ex-
periment of underwater descattering [
6], and the outcome of
the descattered image is pretty good. More recently, Mudge
and Virgen published their real-time polarization dehazing re-
sults using their own polarimetric camera [
14]. The dehazing
algorithm they used is almost the same as Schechner’s. Mean-
while, another dehazing method based on multiresolution
image fusion of color and near-infrared information has also
been reported for haze-degraded images [
15], although it is
much more costly than methods based on the polarimetric im-
aging. Note that, in addition to the above-mentioned physics-
based dehazing methods, there still exist some other
image-processing methods for the same purpose [
16,17].
These methods can also enhance the contrast of hazy images.
However, some information of the image is inevitably lost,
since all these methods estimate the haze of one pixel only
according to several surrounding pixels. In [
17], the authors
compared their result with Schechner’s, and we can easily
see that the latter one is better.
The polarization-based algorithm is very effective in dehaz-
ing; however, there still exist some drawbacks to be
overcome. For one thing, this algorithm is based on two
orthogonal images, which should be the “brightest” and the
“darkest,” respectively, and then adds them together as the
intensity image. This step needs the two images to be exactly
the same; otherwise, there may be ghost shadows in the de-
hazed image and significant details may be submerged in the
background. For another, due to the uncertainty of the CCD
pixels, there always exists the response difference for the
same intensity with two snapshots in one pixel or one
snapshot in different pixels. This may result in terrible noise
in the dehazed image, which needs to be eliminated by com-
plex imaging-processing algorithms. However, such imaging-
processing algorithms may cause some information to be lost.
In this paper, we propose a new polarization dehazing
method. The polarization orientation angle is introduced to
estimate the air light in the image, and it is proved to be quite
useful in eliminating the blur in the dehazed image. Also, the
noise in the sky area can be eliminated without any imaging-
processing algorithm. This algorithm might be much more
convenient and reliable in real-time dehazing.
38 Photon. Res. / Vol. 2, No. 1 / February 2014 Liang et al.
2327-9125/14/010038-07 © 2014 Chinese Laser Press