High spatial and temporal resolution synthetic
aperture phase microscopy
Cheng Zheng,
a,b
Di Jin,
c
Yanping He,
a
Hongtao Lin,
d
Juejun Hu,
e
Zahid Yaqoob,
f
Peter T. C. So,
b,f,g
and
Renjie Zhou
a,h,
*
a
The Chinese University of Hong Kong, Department of Biomedical Engineering, Hong Kong, China
b
Massachusetts Institute of Technology, Department of Mechanical Engineering, Cambridge, Massachusetts, United States
c
Massachusetts Institute of Technology, Computer Science and Artificial Intelligence Laboratory, Cambridge, Massachusetts, United States
d
Zhejiang University, College of Information Science and Electronic Engineering, Hangzhou, China
e
Massachusetts Institute of Technology, Department of Materials Science and Engineering, Cambridge, Massachusetts, United States
f
Massachusetts Institute of Technology, Laser Biomedical Research Center, Cambridge, Massachusetts, United States
g
Massachusetts Institute of Technology, Department of Biological Engineering, Cambridge, Massachusetts, United States
h
The Chinese University of Hong Kong, Shun Hing Institute of Advanced Engineering, Hong Kong, China
Abstract. A new optical microscopy technique, termed high spatial and temporal resolution synthetic aperture
phase microscopy (HISTR-SAPM), is proposed to improve the lateral resolution of wide-field coherent
imaging. Under plane wave illumination, the resolution is increas ed by twofold to around 260 nm, while
achieving millisecond-level temporal resolution. In HISTR-SAPM, digital micromirror devices are used to
actively change the sample illumination beam angle at high speed with high stability. An off-axis
interferometer is used to measure the sample scattered complex fields, which are then processed to
reconstruct high-resolution phase images. Using HISTR-SAPM, we are able to map the height profiles of
subwavelength photonic structures and resolve the period structures that have 198 nm linewidth and
132 nm gap (i.e., a full pitch of 330 nm). As the reconstruction averages out laser speckle noise while
maintaining high temporal resolution, HISTR-SAPM further enables imaging and quantification of nanoscale
dynamics of live cells, such as red blood cell memb rane fluctuations and subcellular structure dynamics within
nucleated cells. We envision that HISTR-SAPM will broadly benefit research in material science and biology.
Keywords: quantitative phase microscopy; label-free imaging; material inspection; cell dynamics observation.
Received Aug. 14, 2020; revised manuscript received Oct. 14, 2020; accepted for publication Nov. 2, 2020; published online
Nov. 26, 2020.
© The Authors. Published by SPIE and CLP under a Creative Commons Attribution 4.0 Unported License. Distribution or
reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
[DOI: 10.1117/1.AP.2.6.065002]
1 Introduction
High-speed and high-resolution imaging techniques have been
long sought for material metrology and biological structure
observation. Such examples include the inspection of large area
subwavelength structures and optical metasurfaces widely used
in integrated photonics,
1,2
monitoring fast semiconduc tor wet
etching process,
3
microdroplet evaporation dynamics,
4
observa-
tion of live cell morphology, fast dynamics in a large
cell population,
5,6
and tracking of high-speed cell motions.
7,8
Conventionally used techniques for material metrology, includ-
ing scanning electron microscop y (SEM) and atomic force
microscopy (AFM), are limited in throughput and speed. In
addition, once the structures are encapsulated in dielectric
claddings, which are the standard practice for photonic devices,
SEM or AFM characterization becomes impractical, as the clad-
ding often obscures the electron imaging contrast between core
and cladding and prohibits physical contact of the AFM probe
with the structure. On the other hand, the challenge for light
microscopy is that many subwavelength structures and living
cells share the common feature of being transparent and thin.
Under conventional bright-field microscopes, those structures
cannot be well resolved due to their weak light absorption.
With chemical staining, fluorescence microscopy can be ap-
plied to imag e these structures. However, for certain live cell
imaging and most material metrology applications, label-free
*Address all correspondence to Renjie Zhou, rjzhou@cuhk.edu.hk
Letter
Advanced Photonics 065002-1 Nov∕Dec 2020
•
Vol. 2(6)