Light Microscopy

1984 ◽  
pp. 267-333
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Dark Field ◽  
Depth Of Field ◽  
Bright Field ◽  
Basic Physics ◽  
Dark Field Illumination ◽  
The Difference ◽  
Tools And Techniques ◽  
The Relationship

Abstract This chapter discusses the tools and techniques of light microscopy and how they are used in the study of materials. It reviews the basic physics of light, the inner workings of light microscopes, and the relationship between resolution and depth of field. It explains the difference between amplitude and optical-phase features and how they are revealed using appropriate illumination methods. It compares images obtained using bright field and dark field illumination, polarized and cross-polarized light, and interference-contrast techniques. It also discusses the use of photometers, provides best practices and recommendations for photographing structures and features of interest, and describes the capabilities of hot-stage and hot-cell microscopes.

scholarly journals Improved Techniques For Imaging Of Three-Dimensional Transparent Specimens In Advanced Darkfield And Interference Contrast Modes

2009 ◽  
Vol 17 (3) ◽  
pp. 20-29
Author(s):  
Jörg Piper
Keyword(s):  
Light Microscopy ◽  
Cell Walls ◽  
Three Dimensional ◽  
Dark Field ◽  
Depth Of Field ◽  
Bright Field ◽  
Dark Field Imaging ◽  
Dark Field Illumination ◽  
Open Position ◽  
Field Imaging

In light microscopy, dark field and interference contrast are widely used for examination of transparent specimens. These methods both suffer from various limitations when photomicrographs have to be taken from fine details, especially in three-dimensional specimens requiring a large depth of field.In common dark field illumination, the condenser either is not equipped with an aperture diaphragm, or an existing condenser diaphragm has to remain in the wide-open position. Thus, the depth of field is lower than in bright field images. Moreover, dark field imaging is associated with marginal blooming, especially in linear structures exhibiting with large differences in phase or density (e.g. cell walls, edges in crystals and other mineralogical material).

Polarimetric Sensing Technique for Textile Material

2016 ◽  
Vol 368 ◽  
pp. 198-202 ◽  
Author(s):  
Michal Vik ◽  
Nayab Khan ◽  
Martina Viková ◽  
František Founě
Keyword(s):  
Polarized Light ◽  
Basic Structure ◽  
Dark Field ◽  
Depth Of Field ◽  
Passive Imaging ◽  
Imaging Polarimetry ◽  
Optical Light Microscopy ◽  
Processing Techniques ◽  
The Relationship ◽  
Geometrical Dimensions

The identification and measuring of geometrical dimensions of very small objects including textile is the biggest achievement of the image processing techniques. Not only the analysis of the basic structure of yarn like hairiness, thickness and number of twist but also the external structural analysis like twist parameters and linear density co-efficient is possible with outstanding approach of image analysis new techniques. Dyed polyester samples by using different dyestuffs were examined with the polarized light with the help of optical light microscopy. It was observed that the dyestuffs possess strong dichroism and the relationship between dichroism and the concentration of dyestuff was examined. Dark field and Bright field illuminations together with imaging polarimetry are compared in terms of depth of field tolerance and image quality. Experiments show that passive imaging polarimetry illumination is superior in terms of depth of field tolerance and contrast allowing significant improvement of textile structure investigation.

Viewing the Specimen Using Reflected-Light Microscopy

2010 ◽  
pp. 89-114
Keyword(s):  
Composite Materials ◽  
Light Microscopy ◽  
Optical Microscopy ◽  
Polarized Light ◽  
Dark Field ◽  
Microscopy Technique ◽  
Reflected Light ◽  
Specific Analysis ◽  
Dark Field Illumination ◽  
Preparation Techniques

Abstract The analysis of composite materials using optical microscopy is a process that can be made easy and efficient with only a few contrast methods and preparation techniques. This chapter is intended to provide information that will help an investigator select the appropriate microscopy technique for the specific analysis objectives with a given composite material. The chapter opens with a discussion of macrophotography and microscope alignment, and then goes on to describe various illumination techniques that are useful for specific analysis requirements. These techniques include bright-field illumination, dark-field illumination, polarized-light microscopy, interference and contrast microscopy, and fluorescence microscopy. The chapter also provides a discussion of sample preparation materials such as dyes, etchants, and stains for the analysis of composite materials using optical microscopy.

scholarly journals OPTICAL EFFECTS AT METALLIC AND NONMETALLIC MATERIALS MICROSCOPY

2018 ◽  
pp. 119-125
Author(s):  
A. G. Anisovich
Keyword(s):  
Surface Defects ◽  
Polarized Light ◽  
Uniaxial Crystal ◽  
Dark Field ◽  
Bright Field ◽  
Visual Classification ◽  
Optical Effects ◽  
Dark Field Illumination ◽  
Transparent Materials

Optical effects arising on surface defects of metals, alloys and transparent materials are discovered in conditions of various illumination such as dark-field and bright-field illumination as well as polarized light. It is shown that the methods of optical contrasting let it possible to determine surface defects of metallic and nonmetallic materials as well as defects inside optically transparent materials. The connection between optical effects and design features of lens by the use of dark-field illumination was shown. It is established that picture generation of spherical defect came about by analogy to uniaxial crystal by the study using polarized light. The schematic diagram of optical effects for various materials to make visual classification of surface defects is suggested.

Microstructural Characterization of CP Steel Used in Automotive Industry

2014 ◽  
Vol 775-776 ◽  
pp. 141-145 ◽  
Author(s):  
Erica Dias ◽  
Laís Horimoto ◽  
Marcelo dos Santos Pereira
Keyword(s):  
Automotive Industry ◽  
Polarized Light ◽  
Microstructural Characterization ◽  
Dark Field ◽  
Metallographic Analysis ◽  
Sodium Metabisulfite ◽  
Bright Field ◽  
Complex Phase ◽  
Dark Field Illumination

This study aims to characterize the microstructure of the complex phase steel (CP). Using the conventional and colored metallographic analysis with 3% Nital etchant, sodium metabisulfite 10% and LePera. Techniques were applied in this work of optical microscopy, using, besides the lighting in bright field, dark field illumination of the reverse contrast in bright field illumination, the method of polarized light, which generates colorful contrast, providing a complementary identification phases present in the microstructure, and the system by differential interference contrast (DIC). The results obtained by metallography CP indicates that the steel has a microstructure composed of ferrite, retained austenite, bainite and martensite and precipitates arranged in a refined and complex morphology. Besides bright field illumination others optical microscopys techniques such as dark field illumination were applied.

Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

1987 ◽  
Vol 45 ◽  
pp. 652-653
Author(s):  
John P. Langmore ◽  
Brian D. Athey
Keyword(s):  
Electron Diffraction ◽  
Phase Contrast ◽  
Low Dose ◽  
Dark Field ◽  
Biological Structure ◽  
Bright Field ◽  
Low Contrast ◽  
Negative Stain ◽  
The Difference ◽  
Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

Resolving Low-Contrast Microstructure Using Transmitted and Reflected Circular Oblique Lighting (COL)

2012 ◽  
Vol 20 (3) ◽  
pp. 38-41 ◽  
Author(s):  
Ted Clarke
Keyword(s):  
Numerical Aperture ◽  
Dark Field ◽  
Resolution Limit ◽  
Hollow Cone ◽  
Bright Field ◽  
Low Contrast ◽  
Dark Field Illumination ◽  
Illumination Method ◽  
Favorable Conditions ◽  
Electron Lithography

A little-known illumination method for light microscopy goes by several names, the most prominent being “circular oblique lighting” (COL) and “hollow-cone illumination”. Matthews notes that hollow-cone or annular bright field illumination can give contrast and resolution superior to that obtainable with narrow-pencil illumination and under favorable conditions comparable to that obtained with phase optics. He demonstrates this with photomicrographs of the same unstained epithelial cell from the mouth mounted in saliva, imaged with a 0.65 numerical aperture (NA) 40× objective. Matthews also notes that the dot pattern of Pleurosigmaangulatum can be resolved with a 0.50 NA objective using circular oblique lighting. Leitz previously marketed the Heine illuminator for transmitted annular (hollow cone) illumination. The NA of the Heine condenser's annular illumination can be adjusted to match the phase annuli in phase contrast objectives. The NA can be increased to provide dark field illumination or circular oblique illumination in bright field. The instructions for the Heine condenser call for the annular illumination just falling within the NA of the objective, what Paul James calls COL and Frithjof A. S. Sterrenberg calls extreme annular illumination, “bright field with very rich contrast.” H. J. Dethloff published a more recent article describing the need for the increased contrast of hollow cone bright field to help resolve the striae of pores in the diatom Amplipleurapellucida. This diatom has been the traditional test of the resolution limit of the light microscope; it is considered a low-contrast subject because the visibility of pores in the transparent amorphous silica frustules is determined by the refractive index difference between the mountant and the frustules. The low contrast makes this a challenging, perhaps even unsuitable, test object for resolution. Resolution tests of modern objectives are done with high-contrast but costly patterns of chrome on glass obtained by electron lithography.

Study of Starch Using Bright Field and Polarized Light Microscopy

2019 ◽  
Author(s):  
Krishna Kant Singh ◽  
Yogendra Yadav ◽  
Deepak Kumar ◽  
Ajitesh Singh ◽  
Debabrata Goswami
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Polarized Light Microscopy ◽  
Bright Field

Structures and defects identified by dark-field HREM

1992 ◽  
Vol 50 (1) ◽  
pp. 124-125
Author(s):  
J.P. Zhang
Keyword(s):  
High Resolution ◽  
Structural Information ◽  
Image Interpretation ◽  
Dark Field Image ◽  
Dark Field ◽  
Bright Field ◽  
Field Mode ◽  
Transmitted Beam ◽  
Structure Information ◽  
The Difference

The tilted illumination dark field high resolution imaging technique was applied to structures and defects of semiconductors and superconductors. We used a Hitachi-H9000 top entry microscope with a high resolution pole-piece of Cs=0.9 mm, operated at 300 Kv. Proper apertures, tilting angle and imaging conditions were chosen to minimize the phase shift due to aberrations. Since the transmitted beam was moved outside the aperture, the noise ratio was greatly reduced, which resulted in a significant enhancement of image contrast and apparent resolution. Images are not difficult to interpret if they have a clear correspondence to structure - information from image simulations in bright field mode can be used to assist in dark field image interpretation.An example in a semiconductor, GaAs/Ga0.49In0.51P2 superlattice imaged along [110] direction is shown in Figure 1. In this dark field image the GaAs and GaInP layers can be easily distinguished by their different contrast, and the difference in quality between both sides of interfaces is clear. An enlarged image in Figure 1 shows the defective area on the rough side of interface. Since this image shows the same pattern as the [110] projection of an fee structure, the major structural information about {111}, {200}, {220} planes can be obtained from this zone. Note that in bright field mode, [110] is not a good zone for imaging such multilayers.

Microcrack Analysis of Composite Materials

2010 ◽  
pp. 159-175
Keyword(s):  
Composite Materials ◽  
Polarized Light ◽  
Fatigue Loading ◽  
Dark Field ◽  
Field Analysis ◽  
Thermal Cycles ◽  
Dynamic Impact ◽  
Bright Field ◽  
Temperature Changes

Abstract The formation of microcracks in composite materials may arise from static-, dynamic-, impact-, or fatigue-loading situations and also by temperature changes or thermal cycles. This chapter discusses the processes involved in the various methods for the microcrack analysis of composite materials, namely bright-field analysis, polarized-light analysis, contrast dyes analysis, and dark-field analysis. The analysis of microcracked composites using epi-fluorescence is also covered. In addition, the chapter describes the procedures for the determination and recording of microcracks in composite materials.

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