Phase Contrast Microscopes

Phase Contrast Microscopy

phasecontrastmicroscopes — Sun, 01 Jul 2007 20:02:32 +0000

Here is an article that discusses about the different features of a phase contrast microscope, its function, and comparison from other types of microscopes, and some interactive tutorials and literature references. Phase contrast microscope is described as a contrast-enhancing optical technique that can be utilized to produce high-contrast images of transparent specimens such as living cells, microorganisms, thin tissue slices, lithographic patterns, and sub-cellular particles, like nuclei and other organelles.

The history of phase contrast microscopy was first realized in 1934 by Dutch physicist Frits Zernike. At some stage in his study of diffraction gratings, he valued both that it is necessary to interfere with a reference beam, and that to maximize the contrast achieved with the technique, it is necessary to introduce a phase shift to this reference so that the no-phase-change condition gives rise to completely destructive interference. The phase contrast system utilizes an optical mechanism to translate minute variations in phase into corresponding changes in amplitude, which can be visualized as differences in image contrast. The phase contrast microscope was awarded with the Nobel Prize in Physics, 1953.
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Fundamentals of Differential Interference Contrast Microscopy

phasecontrastmicroscopes — Tue, 26 Jun 2007 19:20:55 +0000

Here is an article about the fundamentals of differential interference microscopy, and its configuration by the Olympus Microscopy Resource Center.

In the mid-1950s, a French optics theoretician named Georges Nomarski modified the Wollaston prism used for detecting optical gradients in specimens and converting them into intensity differences. Several implementations of this design, which is called differential interference contrast.

Differential interference contrast microscopy, also known as Nomarski Interference Contrast (NIC) or Nomarski microscopy, is an optical microscopy illumination technique used to enhance the contrast in unstained samples. It works on the principle of interferometry to gain information about the optical density of the sample, and to see invisible characteristics. It uses a complex lighting system that produces an image with the object appearing black to white on a grey background, similar to phase contrast microscopy, but without the bright diffraction halo. It is a method of deriving contrast in an unstained specimen from differences in index of refraction of specimen components. (more…)

Phase Contrast and Fluorescent Microscopy

phasecontrastmicroscopes — Sat, 19 May 2007 05:37:33 +0000

Combination of fluorescent microscopy and phase contrast microscopy- while a study of a specimen can be done with a fluorescent microscope or with a phase contrast and still obtain a good result, surely a combination of the two methods would more than double the expected results in terms of clarity and vividness. A primer of epifluorescence microscopy: The fluorescent microscope is used to visualize specimens that fluoresce, that is to say, emit light of a different color, always a higher wavelength, than the light absorbed by the specimen. Fluorescence occurs either because of naturally occurring fluorescent materials in the cells, such as chlorophyll and related molecules or because the cells have been stained with a fluorochrome. Fluorochromes are stains similar to cell and tissues stains used in light microscopy and have been chosen or designed to be highly specific in their attachment to molecules in cells. (more…)

Phase Contrast Microscopy

phasecontrastmicroscopes — Sat, 19 May 2007 05:35:20 +0000

Phase Contrast Microscopy- A vast spectrum of living biological specimen is virtually transparent when observed in the optical microscope under brightfield illumination. However, to improve visibility and contrast in such specimens, microscopists often reduce the opening size of the sub-stage condenser iris diaphragm, but this maneuver is accompanied by a serious loss of resolution and the introduction of diffraction artifacts. Phase contrast was introduced in the 1930s for testing of telescope mirrors, and was adapted by Some laboratories into a commercial microscope several years later. This technique provides an excellent method of improving contrast in unstained biological specimens without significant loss in resolution, and is widely utilized to examine dynamic events in living cells. An overview of Phase Contrast - The search was still on in the early part of the twentieth century to find a way of using both direct and diffracted light from all azimuths to yield good contrast images of unstained objects that do not absorb light. (more…)

Specimen for Phase contrast Microscopes

phasecontrastmicroscopes — Sat, 19 May 2007 05:32:16 +0000

Preparation of specimen in the phase contrast microscope- One may wonder why specimens are to be prepared in phase contrast microscope when staining is done away with and what is being viewed are living objects or live specimen. However, it is not as simple as that, as most specimens are colorless and transparent. Different procedures must be followed to obtain a clear and vivid picture of the specimen Some specimen have to be grown in a monolayer, some have to be fixed to afford a steady observation, and some have to be dissected or sliced appropriately for proper viewing. For studying unstained material, including living cells and tissues, light microscopes with special optical systems, so called phase contrast microscopes are used. In growing cells for study- the cells can be grown in a monolayer directly on a cover slip bathed in cell culture medium for study under a phase contrast microscope. The cell culture medium provides all the nutritional requirements for the cells to divide and prosper. (more…)

Phase Contrast Microscopes

phasecontrastmicroscopes — Sat, 19 May 2007 05:25:54 +0000

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