Quantitative phase-contrast imaging with compact digital holographic microscope employing Lloyd's mirror

Quantitative phase imaging unit

A simple and cost-effective method is presented for quantitative phase imaging. A common-path lateral phase shifting interferometer is realized through attaching a compact filter set to the output port of an existing microscope. The working principles, design criteria, and limitations are also derived and explained. In order to demonstrate the capability and applicability of the method, the optical phase images of a microsphere and individual human red blood cells are measured with high stability.

Digital holographic microscopy with coupled optical fiber trap for cell measurement and manipulation

We present an integrated optical system for three-dimensional (3D) imaging of micrometer-sized samples, while immobilizing and manipulating the samples by means of an optical fiber trap. Optical traps allow us to apply and measure pico-Newton-sized forces, and perform detailed measurements of micrometer-sized dielectric systems in the field of biology. The integrated 3D system can be used as a major tool in the field of biophysics. The trap is built using a tapered optical fiber to enhance the effective numerical aperture of the fiber. The trapping system is mounted on a conventional microscope, in which the two eyepieces' output ports are used as the paths of an off-axis self-referencing digital holographic microscopy (DHM) setup. The trap is calibrated using a high-speed camera, and trap stiffness is determined through the power spectrum method. The compact setup provides an elegant apparatus for temporally stable DHM for 3D imaging of optically controlled samples. Three-dimensional information and quantitative phase contrast images of the trapped samples are obtained by postprocessing the recorded digital holograms. Experiments were performed on lipids and red blood cells. Quantitative phase contrast images and temporal evolution of optical thickness of trapped samples are presented.

Common-path diffraction optical tomography for investigation of three-dimensional structures and dynamics of biological cells

We present an optical holographic micro-tomographic technique for imaging both the three-dimensional structures and dynamics of biological cells. Optical light field images of a sample, illuminated by a plane wave with various illumination angles, are measured in a common-path interferometry, and thus both the three-dimensional refractive index tomogram and two-dimensional dynamics of live biological cells are measured with extremely high sensitivity. The applicability of the technique is demonstrated through quantitative and measurements of morphological, chemical, and mechanical parameters at the individual cell level.

Quantitative phase imaging techniques for the study of cell pathophysiology: from principles to applications

A cellular-level study of the pathophysiology is crucial for understanding the mechanisms behind human diseases. Recent advances in quantitative phase imaging (QPI) techniques show promises for the cellular-level understanding of the pathophysiology of diseases. To provide important insight on how the QPI techniques potentially improve the study of cell pathophysiology, here we present the principles of QPI and highlight some of the recent applications of QPI ranging from cell homeostasis to infectious diseases and cancer.