Forensic Microscopy in the Failure Analysis Laboratory

2000 ◽  
Author(s):  
William E. Vanderlinde ◽  
David A. Stoney
Keyword(s):  
Refractive Index ◽  
Light Microscopy ◽  
Failure Analysis ◽  
Polarized Light ◽  
Optical Microscope ◽  
Dark Field ◽  
Field Methods ◽  
Analysis Laboratory ◽  
Set Up ◽  
Microscopy Techniques

Abstract Optical microscopy techniques used by forensic analysts are shown to have application to failure analysis problems. Proper set up of the optical microscope is reviewed, including the correct use of the field diaphragm and the aperture diaphragm. Polarized light microscopy, bright and dark field methods, refractive index liquids, and a particle reference atlas are used to identify contamination found on semiconductor products.

Light microscopy of ceramics

1993 ◽  
Vol 51 ◽  
pp. 908-909
Author(s):  
Walter C. McCrone
Keyword(s):  
Refractive Index ◽  
Light Microscopy ◽  
Light Microscope ◽  
Polarized Light ◽  
Refractive Indices ◽  
Complete Coverage ◽  
The Subject ◽  
Lower Refractive Index

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).

The release of asbestos fibers from vinyl-asbestos floor tiles

1988 ◽  
Vol 46 ◽  
pp. 968-969
Author(s):  
H.S. MacDonald ◽  
V. M. Kushnaryov ◽  
S. Kolinski ◽  
M. Gallun
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Polarized Light Microscopy ◽  
Drill Bit ◽  
Asbestos Fibers ◽  
Floor Tiles ◽  
Materials Used ◽  
Set Up

There have been extensive studies of the release of asbestos fibers from friable materials used for construction. To date very little is known about the release of asbestos fibers from materials we assume to be non-friable. Since one of the major uses of asbestos was in the manufacture of floor tiles, and flooring is scoured prior to applying sealants, we have studied the release of asbestos from tiles treated in ways which model the processes tiles would be subjected to over their time of use.Vinyl-asbestos tiles were gathered and assayed for their asbestos content by TEM and polarized light microscopy (PLM). Containments were set up and the following experiments performed: 1. 9 inch square tiles were drilled 10 times with a 3/4 inch drill 2. tiles were drilled once with the drill bit above 3. tiles were boken into 1 1/2 inch pieces 4. tiles were broken into 4 pieces 5. tiles were stripped, and then coated with sealants prior to further scrubbing.

scholarly journals Development of Novel Optical Planar Waveguide-based Biosensors using a Nanotechnology Approach

2019 ◽  
Author(s):  
◽  
Ali Madlool Al-Jawdah
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Silicon Nitride ◽  
Planar Waveguide ◽  
Polarization State ◽  
Polarized Light ◽  
Molecular Adsorption ◽  
Low Molecular Weight ◽  
Optical Planar Waveguide ◽  
Set Up

This work aims at the development of novel biosensor based on optical planar waveguide (OPW) for detection of mycotoxins, which are common contaminants in agriculture products (grains, beans, nuts, fruits) and associated food and feed. These low molecular weight toxins produced by various fungi species possess a substantial danger to human and animals, and thus are under strict legislated limits in sub-ppm (part per million) level. The detection of mycotoxins in such low concentrations is of great interest nowadays. A novel detection principle of polarization interferometry (PI) exploited in this system (which can be considered as a logical continuation of ellipsometry) in based on tracking changes in the polarization state of a laser beam passing through the waveguide and affected by immobilized in the waveguide sensing window. The key element of this sensor is a planar optical waveguide consisting of 190 nm thick silicon nitride core layer sandwiched between two thick layers of silicon dioxide; a sensing window was etched in the top silicon oxide layer to allow monitoring molecular adsorption. A 630 nm polarized light from a laser diode coupled through the slant edge of the waveguide experiences a large number of reflections (about 500 per mm) when propagating through the waveguide. The p- component of polarized light is affected by changes in refractive index in the sensing window, while s- component is less affected and thus serves as a reference. Therefore, the changes in either the medium refractive index or molecular adsorption cause the phase shift between p- and s- components. The observation of the light polarization state is enabled by a polarizer converting the changes in polarization to variations of light intensity which is then recoded with CCD linear array interfaced to PC. The refractive index sensitivity of the OPW PI sensor of about 1600 rad/RIU/mm (the highest value known for optical detection) was found by both the theoretical modelling and experimental testing. The developed experimental set-up was used for detection of mycotoxins, i.e. aflatoxin B1 (AFT B1), ochratoxin A (OTA), and zearalenone (ZEN), in direct assay with two types of bio-receptors immobilized within the sensing window: (i) antibodies electrostatically bound onto silicon nitride surface via layers of poly-allylamine hydrochloride and protein A, or (ii) aptamers covalently bound via SH groups on aminated surface of silicon nitride. The outcome of such biosensing tests was successful; all three mycotoxins were detected in a wide concentration range from10 pg/ml up to 1 g/ml in direct immunoassays with their respective antibodies. The use of specific aptamers as bioreceptors in the latest upgrade of the OPW PI set-up has resulted in much lower detected concentrations of AFT B1 and OTA down to 1pg/ml, with LDL estimated as 0.6 -0.7 pg/ml. The obtained sensitivity in sub-ppt (part per trillion) level is the highest known for optical biosensors, and it is particularly remarkable for a label-free detection of low molecular weight analyte molecules in direct assay format. The developed OPW PI biosensor is universal and can be easily adapted for detection of different analyte molecules by choosing suitable bio-receptors. It can be used equally for detection of small and large molecules, and in different assay formats, e.g. direct, sandwich, and competitive assays, and therefore can be considered as a platform biosensing technology for a wide range of applications, i.e. environmental monitoring, security, agriculture and food industry, and biomedical.

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.

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.

Near-field scanning optical microscopy

1986 ◽  
Vol 44 ◽  
pp. 642-643
Author(s):  
E. Betzig ◽  
A. Harootunian ◽  
M. Isaacson ◽  
A. Lewis
Keyword(s):  
Near Field ◽  
Optical Microscope ◽  
Visible Radiation ◽  
Field Methods ◽  
Optical Elements ◽  
Optical Region ◽  
Order Of Magnitude ◽  
Nondestructive Imaging ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

On resolving fine periodic microstructures in the optical microscope

1989 ◽  
Vol 47 ◽  
pp. 364-365
Author(s):  
W.S. Putnam ◽  
C. Viney
Keyword(s):  
Liquid Crystalline ◽  
Numerical Aperture ◽  
Polarized Light ◽  
Normal Incidence ◽  
Optical Microscope ◽  
Angle Of Incidence ◽  
Resolution Limit ◽  
Crystalline Materials ◽  
Periodic Microstructures ◽  
Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

Imaging sub-micron objects with light microscopy: Visualization of the T-4 bacteriophage

1989 ◽  
Vol 47 ◽  
pp. 834-835
Author(s):  
Malcolm Brown ◽  
Reynolds M. Delgado ◽  
Michael J. Fink
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Focal Plane ◽  
Phase Contrast ◽  
Dark Field ◽  
E Coli ◽  
Polystyrene Beads ◽  
Television Camera ◽  
Transmission Electron ◽  
Universal Microscope

While light microscopy has been used to image sub-micron objects, numerous problems with diffraction-limitations often preclude extraction of useful information. Using conventional dark-field and phase contrast light microscopy coupled with image processing, we have studied the following objects: (a) polystyrene beads (88nm, 264nm, and 557mn); (b) frustules of the diatom, Pleurosigma angulatum, and the T-4 bacteriophage attached to its host, E. coli or free in the medium. Equivalent images of the same areas of polystyrene beads and T-4 bacteriophages were produced using transmission electron microscopy.For light microscopy, we used a Zeiss universal microscope. For phase contrast observations a 100X Neofluar objective (N.A.=1.3) was applied. With dark-field, a 100X planachromat objective (N.A.=1.25) in combination with an ultra-condenser (N.A.=1.25) was employed. An intermediate magnifier (Optivar) was available to conveniently give magnification settings of 1.25, 1.6, and 2.0. The image was projected onto the back focal plane of a film or television camera with a Carl Zeiss Jena 18X Compens ocular.

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