CPB Online In-PressCPB Online In-Press
Chin. Phys. B Vol. 26, No. 2 (2017) 024203
Sub-Rayleigh imaging via undersampling scanning based on
sparsity constraints
∗
Chang-Bin Xue(薛长斌)
1,2
, Xu-Ri Yao(姚旭日)
2,†
, Long-Zhen Li(李龙珍)
2
, Xue-Feng Liu(刘雪峰)
2
,
Wen-Kai Yu(俞文凯)
1
, Xiao-Yong Guo(郭晓勇)
2,‡
, Guang-Jie Zhai(翟光杰)
2
, and Qing Zhao(赵清)
1
1
School of Physics, Beijing Institute of Technology, Beijing 100081, China
2
Key Laboratory of Electronics and Information Technology for Space System, National Space Science Center,
Chinese Academy of Sciences, Beijing 100190, China
(Received 29 August 2016; revised manuscript received 11 October 2016; published online 10 January 2017)
We demonstrate that, by undersampling scanning object with a reconstruction algorithm related to compressed sens-
ing, an image with the resolution exceeding the finest resolution defined by the numerical aperture of the system can be
obtained. Experimental results show that the measurements needed to achieve sub-Rayleigh resolution enhancement can be
less than 10% of the pixels of the object. This method offers a general approach applicable to point-by-point illumination
super-resolution techniques.
Keywords: super-resolution, image reconstruction techniques
PACS: 42.40.Lx, 42.30.Va DOI: 10.1088/1674-1056/26/2/024203
1. Introduction
A widely used criterion to define the spatial resolution of
a diffraction-limited imaging system is the so-called Rayleigh
limit which sets the minimum separation for two points to be
distinguishable in the image. The Rayleigh diffraction bound
is related to the width of the point spread function (PSF)
of the optical instrument, and the image is obtained by con-
volving the PSF with the transmission function of the object.
The super-resolution, which refers to methods for improving
the resolution of optical imaging system beyond the Rayleigh
limit, has been a topic of great interest for more than a century.
The use of scanning is very common in super-resolution meth-
ods such as confocal scanning microscopy.
[1,2]
Generally in
confocal scanning fluorescence microscopy systems, the light
source should be powerful so that it can still reach the detec-
tor when a pinhole is placed to limit the radius of the light.
The accurate movement of the pinhole based on the focused
beam cannot be achieved under particular circumstances.
[3]
The scanning time also is unfavorable for achieving real-time
observation.
Recently, an information processing technique known
as compressed sensing (CS),
[4,5]
which employs optimiza-
tion to detect a sparse n-dimensional signal with m < n mea-
surements, has been utilized in many optical schemes.
[6–8]
The sparsity-based concepts of CS have also been taken into
the super-resolution domain, and dramatic performances have
been revealed.
[9–13]
The implementations of the single-pixel
camera,
[6]
which is a successful application of CS, in fluo-
rescence microscopy benefits from many advantages such as
high dynamic range, facilitated multiplexing, and wide spec-
tral range (from ultraviolet range to infra-red range).
[14]
In this paper we demonstrate another approach that com-
bines focused scanning with a reconstruction algorithm related
to CS to achieve super-resolution images borne on incoherent
light with theoretical analysis and experimental proof. In this
method, different from the conventional focused illumination
super-resolution methods which mainly try to narrow the PSF
of the system, the sparsity of the object and the PSF of opti-
cal imaging system are utilized as priori knowledge to recover
the information of the object. The measurements needed to
achieve sub-Rayleigh resolution enhancement can be less than
10% of the pixels of the object. The conventional compressive
fluorescence microscopy configurations mentioned above also
can benefit from this scheme since it does not require modify-
ing the experimental apparatus.
2. Image reconstruction methods
If we denote the object as an n-dimensional vector x, then
the data acquisition by scanning can be described as
y = A · x, (1)
where A is the scanning matrix, namely, an n-by-n identity
matrix, and y is the intensities measured. In an ideal imaging
∗
Project supported by the National Natural Science Foundation of China (Grant Nos. 61605218 and 61601442), the National Defense Science and Technology
Innovation Foundation of the Chinese Academy of Sciences (Grant No. CXJJ-16S047), and the National Major Scientific Instruments Development Project of
China (Grant No. 2013YQ030595).
†
Corresponding author. E-mail: yaoxuri@aliyun.com
‡
Corresponding author. E-mail: xyguo@nssc.ac.cn
© 2017 Chinese Physical Society and IOP Publishing Ltd http://iopscience.iop.org/cpb http://cpb.iphy.ac.cn
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