Tomographic Phase Microscopy (TPM) - Biomedical Optical Phase Microscopy and Nanoscopy - page 222

CHAPTER 12
Tomographic Phase Microscopy (TPM)
Wonshik Choi
Department of Physics, Korea University, Seoul, Korea
Editor: Natan T. Shaked
12.1 Introduction
Conventional interferometric microscopy techniques such as digital holographic microscopy
and quantitative phase microscopy are classified as three-dimensional (3D) imaging
techniques because a recorded complex field image can be numerically propagated to a
different depth. Strictly speaking, however, a single complex field image contains only
two-dimensional (2D) information on a specimen because the measured 2D image is
only a subset of the 3D structure. In this chapter, we introduce tomographic phase
microscopy (TPM) that experimentally implements optical diffraction tomography (ODT)
suggested by Wolf in 1969 [1,2] for the 3D mapping of living specimens. The TPM enables
us to record complex field images of a specimen at various angles of illumination. And the
ODT makes it possible to reconstruct the 3D structure of a specimen from the multiple
angle-dependent or wavelength-dependent complex field images. By mapping the acquired
multiple independent 2D images onto the 3D Fourier space of the specimen, a tomographic
map of the absorption coefficient and refractive index can be reconstructed. Since the
refractive index is a measure of the molecular concentration, the tomographic map of the
refractive index in a single intact living cell has drawn many interesting biomedical
applications. In the latter part of this chapter, applications including quantitative assessment
of disease progression in malaria-infected red blood cells (RBCs) are covered.
Refractive index serves as an important intrinsic contrast agent in visualizing nearly
transparent living biological cells. Examples include phase contrast microscopy [3] and
differential interference microscopy [4] , which have been widely used in cell biology
studies. In essence, both techniques make use of optical interferometry to enhance the
contrast. Interferometry converts phase changes of the transmitted wave induced by the
heterogeneous refractive index distribution within the cell into intensity variations.