Super-resolution imaging in digital holography by using dynamic
grating with a spatial light modulator
Qiaowen Lin
a,b
, Dayong Wang
a,c,
n
, Yunxin Wang
a,c,
n
, Lu Rong
a,c
, Shifeng Chang
a
a
College of Applied Sciences, Beijing University of Technology, No. 100 Pingleyuan Rd, Beijing 100124, China
b
School of Physics and Electronics Science, Shanxi Datong University, Datong 037009, Shanxi, China
c
Institute of Information Photonics Technology, Beijing University of Technology, Beijing 100124, China
article info
Article history:
Received 7 June 2014
Received in revised form
17 September 2014
Accepted 23 September 2014
Available online 24 October 2014
Keywords:
Digital holography
Super-resolution
Grating
Spatial light modulator
abstract
A super-resolution imaging method using dynamic grating based on liquid-crystal spatial light
modulator (SLM) is developed to improve the resolution of a digital holographic system. The one-
dimensional amplitude cosine grating is loaded on the SLM, which is placed between the object and
hologram plane in order to collect more high-frequency components towards CCD plane. The point
spread function of the system is given to confirm the separation condition of reconstructed images for
multiple diffraction orders. The simulation and experiments are carried out for a standard resolution test
target as a sample, which confirms that the imaging resolution is improved from 55.7
μ
mto31.3
μ
m
compared with traditional lensless Fourier transform digital holography. The unique advantage of the
proposed method is that the period of the grating can be programmably adjusted according to the
separation condition.
& 2014 Elsevier Ltd. All rights reserved.
1. Introduction
In digital holography (DH), the hologram is recorded by a CCD
or a CMOS camera instead of the traditional photosensitive
materials, and the reconstruction is performed numerically. DH
has growing applications in biological cell imaging, microstructure
detection, particle field analysis, and temperature field measure-
ment etc. [1–6]. The resolution of a digital holographic system is
directly related to the numerical aperture (NA) of the recording
device and the wavelength used in the recording. Because of the
finite aperture of the imaging system, only the low-frequency
parts of the object spectrum are recorded by the CCD. As a result,
the corresponding reconstructed images are band-limited in the
frequency domain. Therefore the improvement of the resolution in
digital holography is the main research focus [7–18].
To improve the resolution, researchers ha v e lately intr oduced
super-resolution t echniq ues int o digital holograph ic imaging. Ale x-
androv et al. rotated the sample and recorded a digital hologram for
each position to enhance the resolution [7]. Massing et al. recorded
nine holograms by translating CCD to different positions to improv e
the resolution [8]. Mico et al. utilized the tilted illumination and
common-path interferometric recording to enhance the resolution of
the imaging system [1 2]. These methods need to record multiple
digital holograms by moving op tical elements manually , and the
object position must be fixed during the recording. Therefore, the
high stability of the system is deman ded. How ever it is not easy to
meet this rigid demand in a practical environment. Fortunately ,
grating technology only needs to recor d one hologram, which is
reconstructed by subsequent numerical processing in order to get
more information on the object wav e, and the experime nta l set-up is
simple and stab le. Liu et al. demonstrated that placi ng a gr ating in
front of the specimen means high fre q uency diffracted object wa ves
can reach the CCD to improve the resolution [16]. Paturzo et al.
specially designed an electro-op tical two-dimen sional gratin g in
their lab t o improve the resolution [1 8],buttheirgratingisnot
av aila ble commercially. At present, the diffraction propagation theory
using grating for super-r esolution imaging need to be further studied
and the separation conditions of numerical r econstructed images
for multiple diffraction orders of the object wave hav e not been
quantita tiv el y analyzed. The key to super-r esolution imaging with
grating technol ogy is to optimize the experimental paramet ers in
the configuration system. If a fix ed grating is used for the super-
resolution imaging, the adjustment of experimental parameters is
often more complicated and the field of view of the imaging system
cannot be adjusted flexibly.
In this paper , we analyze the point spread function of the system
and confirm the separation condition of reconstructed images for
multiple diffraction orders. Then the SLM is applied to realiz e the
periodic amplitude grating which can be dynamically adjusted by
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/optlaseng
Optics and Lasers in Engineering
http://dx.doi.org/10.1016/j.optlaseng.2014.09.015
0143-8166/& 2014 Elsevier Ltd. All rights reserved.
n
Corresponding authors at: College of Applied Sciences, Beijing University of
Technology, No. 100 Pingleyuan Rd, Beijing 100124, China. Tel.: þ86 1067391741.
E-mail addresses: wdyong@bjut.edu.cn (D. Wang),
yxwang@bjut.edu.cn (Y. Wang).
Optics and Lasers in Engineering 66 (2015) 279–284