3D imaging by two-color Ewald spheres
with optical lasers
Jian Zhang (张 剑)
1
, Jiadong Fan (范家东)
1
, Jianhua Zhang (张建华)
1
,
Qingjie Huang (黄庆捷)
2
, and Huaidong Jiang (江怀东)
1,3,
*
1
State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
2
School of Information Science and Engineering, Shandong University, Jinan 250100, China
3
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
*Corresponding author: hdjiang@sdu.edu.cn
Received May 7, 2016; accepted September 29, 2016; posted online October 27, 2016
3D imaging techniques such as computed tomography, ultrasonography, and magnetic resonance imaging
usually combine many scans computationally. Here, we report a 3D imaging approach using an optical-laser
diffraction microscope with two different wavelength lasers in the same orientation. A double-layered sample
constructed of silica spheres is used for coherent diffraction imaging with two lasers at 543 and 432 nm. The
diffraction patterns obtained using a planar detector at a high numerical aperture are projected onto the Ewald
spheres. 3D images of the double-layered sample are successfully reconstructed from the two-color spherical
diffraction patterns.
OCIS codes: 110.1650, 110.6880, 100.5070.
doi: 10.3788/COL201614.111102.
Pursuing a high spatial and temporal resolution is criti-
cally important to investigating 3D structures and
dynamics in material science, physics, and biology
[1–4]
.
However, 3D reconstruction of objects usually requires
a series of projections at different angles, depths, over-
lapped positions, or a large number of copies
[5–7]
.Itisa
challenging task to study the dynamic 3D imaging by
conventional methods, especially for biological cells in
their natural state and nanoparticles
[8]
, which are easily
damaged by high-energy radiation
[9]
. Recently, a novel
single-orientation 3D imaging technique based on coher-
ent diffraction imaging (CDI)
[10]
has been developed to sur-
pass the challenges
[11]
. An algorithmic reconstruction of 3D
imaging of objects can be obtained from Ewald spherical
shells, which is derived from the measured 2D diffraction
patterns on a planar CCD detector. Previous studies have
demonstrated the 3D imaging of objects using soft X-ray
and optical lasers
[11–13]
. Although some progress has been
made, the 3D imaging method still faces challenges in im-
aging of large or thick objects due to limited information in
reciprocal space, which also caused some arguments
[14,15]
.
Recently, a sparsity-based approach has been attracted
to recover the 3D molecu lar structures
[16]
. Some research-
ers proposed volume optics, which is designed by a volu-
metric scattering approach based on the concept of an
Ewald sphere
[17]
. In spite of these methods to recover
the 3D images of objects, multiwavelength diffraction
patterns provide more information to improve the conver-
gence speed during reconstructions and enhance the qual-
ity of coherent imaging. This strategy is easily realized
with energy-resolved detectors for optical laser micros-
copy, even for X-ray free electron laser (XFEL) diffraction
imaging
[18]
. With the development of multiwavelength
XFEL
[19]
, new methods based on diffraction imaging
become essential.
In this Letter, we experimentally demonstrated for the
first time an approach to recover the 3D image of an object
using two Ewald spheres with high numerical apertures.
The result indicates that utilizing multiple-wavelength la-
ser sources for deciphering the 3D image of materials has
potential applications in single-orientation measurement.
A general schematic diagram for the imaging of 3D ob-
jects is shown in Fig.
1. The experiment was carried out
using a laser diffraction microscope with two lasers in the
same orientation. The intensity of the laser beams was
attenuated by neutral density filters and then passed
through two convergence lenses with focal lengths of
1500 and 500 mm. The attenuation coefficient of a
neutral density filter depends on the power of the laser
used. The beam illuminated on the sample ensures a pla-
nar wavefront. Two apertures were positioned behind the
lens to eliminate unwanted scattering of laser beams.
To acquire light scattering from objects, we used a liquid
Fig. 1. Schematic diagram of a coherent diffraction microscope
with two lasers at 543 (green) and 432 nm (blue) in the same
orientation.
COL 14(11), 111102(2016) CHINESE OPTICS LETTERS November 10, 2016
1671-7694/2016/111102(4) 111102-1 © 2016 Chinese Optics Letters