Chapter 1
Quantitative Phase Imaging: Principles
and Applications
Chenfei Hu and Gabriel Popescu
Abstract Quantitative phase imaging (QPI) is an emerging label-free imaging
approach. QPI measures the optical phase delay associated with the object, and
the resulting image provides an objective measure of morphology and dynamics,
in the absence of contrast agents. As tremendous advances have been made in the
past one–two decades, the QPI field continues expanding and gaining popularity.
It has found applications in many different fields, especially in biomedicine. In this
chapter, we provide a review of the principles associated with this exciting field, with
discussion focused on optical physics, experimental principles, and applications.
1.1 Introduction
The phase of a scattered filed is of great interest, as it carries information about
the internal structure of the specimen under investigation [1, 2]. In microscopy,
biological samples (e.g., cells and tissue slices) exhibit low absorption in the visible
spectrum. Thus, it is the phase change rather than the amplitude of the field that
provides an intrinsic contrast mechanism. Zernike and Nomarski are the pioneers
exploiting the phase imaging concept. Their inventions, phase-contrast microscopy
(PCM), and differential interference contrast (DIC) microscopy, respectively, reveal
the inner details of transparent specimen without exogenous staining or fluorescent
tagging, which has been widely used in biological laboratories worldwide [3–5].
However, these early methods only produce intensity images, where the complex
field information, i.e., the amplitude and phase, cannot be retrieved uniquely. On the
other hand, in the 1940s, Gabor proved the concept that a complex optical field can
be stored and reconstructed by using principles of holography [6, 7].
C. Hu · G. Popescu (B)
Quantitative Light Imaging Laboratory, Electrical and Computer Engineering, Beckman Institute
for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL
61801, USA
e-mail: gpopescu@illinois.edu
© Springer Nature Switzerland AG 2019
V. Astratov (ed.), Label-Free Super-Resolution Microscopy,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-3-030-21722-8_1
1
Quantitative Phase Imaging: Principles
and Applications
Chenfei Hu and Gabriel Popescu
Abstract Quantitative phase imaging (QPI) is an emerging label-free imaging
approach. QPI measures the optical phase delay associated with the object, and
the resulting image provides an objective measure of morphology and dynamics,
in the absence of contrast agents. As tremendous advances have been made in the
past one–two decades, the QPI field continues expanding and gaining popularity.
It has found applications in many different fields, especially in biomedicine. In this
chapter, we provide a review of the principles associated with this exciting field, with
discussion focused on optical physics, experimental principles, and applications.
1.1 Introduction
The phase of a scattered filed is of great interest, as it carries information about
the internal structure of the specimen under investigation [1, 2]. In microscopy,
biological samples (e.g., cells and tissue slices) exhibit low absorption in the visible
spectrum. Thus, it is the phase change rather than the amplitude of the field that
provides an intrinsic contrast mechanism. Zernike and Nomarski are the pioneers
exploiting the phase imaging concept. Their inventions, phase-contrast microscopy
(PCM), and differential interference contrast (DIC) microscopy, respectively, reveal
the inner details of transparent specimen without exogenous staining or fluorescent
tagging, which has been widely used in biological laboratories worldwide [3–5].
However, these early methods only produce intensity images, where the complex
field information, i.e., the amplitude and phase, cannot be retrieved uniquely. On the
other hand, in the 1940s, Gabor proved the concept that a complex optical field can
be stored and reconstructed by using principles of holography [6, 7].
C. Hu · G. Popescu (B)
Quantitative Light Imaging Laboratory, Electrical and Computer Engineering, Beckman Institute
for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL
61801, USA
e-mail: gpopescu@illinois.edu
© Springer Nature Switzerland AG 2019
V. Astratov (ed.), Label-Free Super-Resolution Microscopy,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-3-030-21722-8_1
1