Digital Holographic Interference Microscope Research Articles

Compact, low cost, large field-of-view self-referencing digital holographic interference microscope

Digital holographic microscopes provide quantitative phase images of transparent objects like biological cells. These phase images can in turn provide a host of parameters based on the object morphology, which could be used for object identification. But one of the biggest challenges in digital holographic microscopy is the design of compact setups with minimal optical elements providing high quality images and nanometer level temporal stability. Self-referencing interferometers in which the reference beam is obtained from the object beam is ideal for implementing compact devices with only few optical components. But they suffer from reduced field of view and has restriction on the sparsity of object distribution. Here we describe the development of a low-cost large field of view self-referencing digital holographic microscope based on wavefront division interferometer utilizing Lloyd’s mirror geometry. The device takes away the restriction on the sparsity of the sample also. The developed device does not have any translation stage and the focusing is achieved post-recording of the holograms. Off the shelf low-cost optics, a laser pointer and a webcam were used in development of the device. The developed device was tested on glass microspheres as well as was used to study human erythrocytes. To the best of our knowledge this is the first time such low-cost configuration using webcam is demonstrated for quantitative phase imaging of cells.

Wide field of view common-path lateral-shearing digital holographic interference microscope.

Quantitative three-dimensional (3-D) imaging of living cells provides important information about the cell morphology and its time variation. Off-axis, digital holographic interference microscopy is an ideal tool for 3-D imaging, parameter extraction, and classification of living cells. Two-beam digital holographic microscopes, which are usually employed, provide high-quality 3-D images of micro-objects, albeit with lower temporal stability. Common-path digital holographic geometries, in which the reference beam is derived from the object beam, provide higher temporal stability along with high-quality 3-D images. Self-referencing geometry is the simplest of the common-path techniques, in which a portion of the object beam itself acts as the reference, leading to compact setups using fewer optical elements. However, it has reduced field of view, and the reference may contain object information. Here, we describe the development of a common-path digital holographic microscope, employing a shearing plate and converting one of the beams into a separate reference by employing a pin-hole. The setup is as compact as self-referencing geometry, while providing field of view as wide as that of a two-beam microscope. The microscope is tested by imaging and quantifying the morphology and dynamics of human erythrocytes.

Combining the polarization-contrast and interference-contrast methods for three-dimensional visualization of anisotropic microobjects

This paper presents a theoretical and experimental study of the possibilities of using a holographic method of polarization contrast to solve the problem of three-dimensional visualization of anisotropic microobjects. The experimental studies were carried out using a digital holographic interference microscope. It is shown that the polarization-contrast method makes it possible to obtain three-dimensional images of anisotropic microobjects with the maximum contrast and high quality, and this increases the sensitivity and resolution of the method by comparison with other optical methods. The possibilities of combining holographic methods of polarization contrast and interference contrast for the three-dimensional visualization of anisotropic microobjects have been studied for the first time.

Application of the Digital Holographic Interference Microscopy for Thin Transparent Films Investigation

Abstract In this work the digital holographic interference microscope (DHIM) is proposed for investigation of thin transparent films on transparent substrates. The DHIM allows 3D imaging of surfaces of thin transparent films, and measurement of their geometrical parameters (thicknesses, sizes of defects). The method of the holographic interferometry, and the optical layout of the DHIM are described. The experimental results of investigation of thin AlN coatings on acryl substrates are presented.

Holographic Method for Blood Cell Imaging

Human blood cells (erythrocytes) were imaged by the digital holographic interference microscope (DHIM) without any preparation. DHIM represents an effective technique for 3D imaging of phase microscopic objects and measurement of their morphological parameters. It has been detected that, in addition to hematological diseases, the diseases of different genesis and external factors serve as the reason for the morphological modification of blood erythrocytes.

Using digital holographic microscopy to study transparent thin films

This paper presents the first experimental results of using a digital holographic interference microscope (DHIM) to study thin transparent films (with thickness less than the wavelength of visible light) on transparent substrates. The DHIM makes it possible not only to obtain a three-dimensional image of the film surface, but also to carry out quantitative measurements. Coatings composed of aluminum nitride (AlN) on acrylic substrates are used as the films, which can be used to protect items made from acryl from the action of the surroundings. Surface defects existing on the surface of the coatings and resulting from the action of UV radiation on the coating and the substrate have been studied. The method of classical optical microscopy for investigating thin transparent films has been compared with the possibilities of the method of digital holographic microscopy. The results confirmed that it is efficient to use DHIM for such studies.

Digital holographic interference microscopy in the study of the 3D morphology and functionality of human blood erythrocytes

A digital holographic interference microscope is used to experimentally study the 3D morphology of human blood erythrocytes. It is demonstrated that, in addition to hematological diseases, the diseases of various genesises and external factors serve as the reasons for the morphological modifications of blood erythrocytes. A 3D model of erythrocyte is proposed to quantitatively estimate the effect of morphological modifications of blood erythrocytes on their functionality with respect to the oxygen transfer. It is demonstrated that the observed morphological modifications of erythrocytes lead to a significant decrease in the blood oxygen capacity and can serve as a reason for hypoxia.

Digital holographic interference microscopy in the study of the 3D morphology and functionality of human blood erythrocytes

A digital holographic interference microscope is used to experimentally study the 3D morphology of human blood erythrocytes. It is demonstrated that, in addition to hematological diseases, the diseases of various genesises and external factors serve as the reasons for the morphological modifications of blood erythrocytes. A 3D model of erythrocyte is proposed to quantitatively estimate the effect of morphological modifications of blood erythrocytes on their functionality with respect to the oxygen transfer. It is demonstrated that the observed morphological modifications of erythrocytes lead to a significant decrease in the blood oxygen capacity and can serve as a reason for hypoxia.

Holographic interference microscope for laboratory studies

A digital holographic interference microscope is designed that allows real-time 3D imaging of phase microobjects and measurement of their morphological parameters. The instrument may find application in medical institutions and research laboratories.