Method of Making Micro-Sections of Rubber Stocks

1930 ◽  
Vol 3 (4) ◽  
pp. 755-763
Author(s):  
Raymond P. Allen
Keyword(s):  
Field Work ◽  
Dark Field ◽  
The Other ◽  
Bright Field ◽  
Thin Sections ◽  
Rubber Compounds ◽  
Dark Field Illumination ◽  
Natural Belief ◽  
Rubber Stock ◽  
Highly Loaded

Abstract THE possibility of seeing pigment particles in a rubber stock has always been a desire of rubber chemists. There has been a natural belief that if the particles in rubber could actually be observed with a microscope more could be learned about their action and properties. The main difficulty in attaining this end lies in the preparation of sufficiently thin sections. For clear observation of highly loaded gas-black stocks the sections must be less than 1 micron thick. For bright-field work with light-colored or colorless pigments, such as litharge and zinc oxide, the sections may be somewhat thicker. However, if the examination is to be made with dark-field illumination the sections for even the colorless pigments must again be very thin. Several methods have been proposed and utilized for making thin sections, and the names of Dannenberg (2), Depew (3), Green (4), Grenquist (5), Hauser (7), Moore (11), Pohle (9), Ruby (3), Spear (11), and Walton (12) are identified with the skilful manipulation which is necessary for achieving the desired result. There have been many other workers in this field, including Weber (13), Breuil (1), Loewen (8), Regnaud (10), and Hardman (6). The method to be described was developed in this laboratory in 1926. It has been used continually since that time and has proved valuable in the study of rubber compounds and pigments. While it bears a slight similarity to some of the other methods, it has certain unique and distinct advantages of its own.

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.

scholarly journals Multiangle Long-Axis Lateral Illumination Photoacoustic Imaging Using Linear Array Transducer

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 4052
Author(s):  
João H. Uliana ◽  
Diego R. T. Sampaio ◽  
Guilherme S. P. Fernandes ◽  
María S. Brassesco ◽  
Marcello H. Nogueira-Barbosa ◽  
...  
Keyword(s):  
Fiber Bundle ◽  
Linear Array ◽  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Dark Field ◽  
Bright Field ◽  
Light Delivery ◽  
Array Transducer ◽  
Dark Field Illumination ◽  
Lateral Illumination

Photoacoustic imaging (PAI) combines optical contrast with ultrasound spatial resolution and can be obtained up to a depth of a few centimeters. Hand-held PAI systems using linear array usually operate in reflection mode using a dark-field illumination scheme, where the optical fiber output is attached to both sides of the elevation plane (short-axis) of the transducer. More recently, bright-field strategies where the optical illumination is coaxial with acoustic detection have been proposed to overcome some limitations of the standard dark-field approach. In this paper, a novel multiangle long-axis lateral illumination is proposed. Monte Carlo simulations were conducted to evaluate light delivery for three different illumination schemes: bright-field, standard dark-field, and long-axis lateral illumination. Long-axis lateral illumination showed remarkable improvement in light delivery for targets with a width smaller than the transducer lateral dimension. A prototype was developed to experimentally demonstrate the feasibility of the proposed approach. In this device, the fiber bundle terminal ends are attached to both sides of the transducer’s long-axis and the illumination angle of each fiber bundle can be independently controlled. The final PA image is obtained by the coherent sum of subframes acquired using different angles. The prototype was experimentally evaluated by taking images from a phantom, a mouse abdomen, forearm, and index finger of a volunteer. The system provided light delivery enhancement taking advantage of the geometry of the target, achieving sufficient signal-to-noise ratio at clinically relevant depths.

The Dark Field Cut Surface (DFCS) Test for Estimating the Dispersion of Carbon Black in Rubber Compounds

1997 ◽  
Vol 70 (1) ◽  
pp. 50-59 ◽  
Author(s):  
G. A. W. Murray ◽  
D. W. Southwart ◽  
P. K. Freakley
Keyword(s):  
Carbon Black ◽  
Numerical Estimate ◽  
Dark Field ◽  
Field Of View ◽  
High Magnification ◽  
Ability To Work ◽  
Rubber Compounds ◽  
Dark Field Illumination ◽  
Cut Surface ◽  
Initial Results

Abstract A test for estimating the dispersion of carbon black in rubber compounds is described. It works by examining the freshly cut surface of a specimen at low magnification in dark field illumination. Roughness of the surface related to the presence of carbon black causes increased reflection under dark field illumination. The illumination of each field of view is examined as 100 subdivisions and the relative values of these readings give a numerical estimate of the dispersion. Details of how this is done and the corrections applied to the results are described. A second paper reports some initial results obtained with the test. The test works well for certain elastomers, notably NR and SBR. The biggest advantage of the test is its ability to work rapidly and cheaply on small zones at relatively high magnification. This opens up the possibility of detailed studies of macroscopic variations in dispersion, done in reasonable times and at reasonable costs.

A Study on Heat History of Organic Accelerators in Rubber Stock (BR Base)

1970 ◽  
Vol 43 (4) ◽  
pp. 799-828
Author(s):  
I. Imase
Keyword(s):  
The Other ◽  
Frictional Heat ◽  
Rubber Matrix ◽  
Rubber Compound ◽  
Incremental Effect ◽  
Rubber Compounds ◽  
History Of ◽  
Curing Agents ◽  
Heat History ◽  
Rubber Stock

Abstract Rubber with some exceptions must generally undergo such processes as mastication, mixing, warming-up, extrusion, spreading, calendering, etc. prior to vulcanization under heat to obtain cured articles. Consequently the rubber matrix receives a heat history caused by mechanical frictional heat or the heat which cannot be avoided during these processes. On the other hand, when an uncured rubber compound, ready for vulcanization, containing such curing agents as sulfur, such activators as zinc oxide, and organic accelerators is heated during the processes or during storage between individual processes, each incremental effect of heat is accumulated with time. It is a well-known fact that this accumulation of heat can lead to the trouble of scorching, etc. As a cause for the trouble, organic accelerators seem to play the most important role. A few reports have been published on the action of accelerators under heat, but, to my knowledge, no report is available on the behavior of accelerators in rubber stocks, namely, on the change of the properties of uncured rubber compounds and on its influence on the properties of vulcanizates. This paper shall report these problems, though it describes only the results of the tests carried out under specific conditions.

Diffraction contrast and defect symmetry

1978 ◽  
Vol 36 (1) ◽  
pp. 180-181
Author(s):  
K.-H. Katerbau
Keyword(s):  
Displacement Field ◽  
Lattice Defect ◽  
Reciprocal Lattice ◽  
Dark Field ◽  
The Other ◽  
Foil Thickness ◽  
Foil Surface ◽  
Bright Field ◽  
Incident Electron Beam ◽  
Cartesian Coordinate

Symmetry rules for the bright-field images of lattice defects were derived by Howie and Whelan /1 /, and for the dark-field images by Pogany and Turner /2/. In both cases, only one of the N diffracted beams is considered, and no statement is made on how the intensities of the other beams are affected by defect symmetry. This question is studied in the present paper.We make use of the column approximation and assume a centro-symmetric crystal and N reflections gn (n=o,...N-1 with go=o), lying in the same reciprocal lattice plane.A cartesian coordinate system (x,y,z) is introduced with the x- and y-axes in this plane and the origin in the centre of the lattice defect, located at a distance zo below the upper foil surface, t is the foil thickness, R(x,y,z) the displacement field of the defect with the abbreviation. R(z) for the displacement field at the column (x,y), and k = (kx, ky ) is the component of the wave vector of the incident electron beam in the (x,y)- plane. k=-gj/2 means that g. is in the Bragg reflecting position.

A Quantitative Study of Illumination Techniques for Machine Vision Based Inspection

2011 ◽  
Author(s):  
Michael T. Yan ◽  
Brian W. Surgenor
Keyword(s):  
Machine Vision ◽  
Quantitative Study ◽  
Dark Field ◽  
Vision Systems ◽  
Bright Field ◽  
Dark Field Illumination ◽  
Quantitative Performance ◽  
Sample Set ◽  
Inspection Task

In this paper, three basic lighting geometries are compared quantitatively in an inspection task that checks for the presence of J-clips on an aluminum carrier. Two independent LabVIEW® machine vision algorithms were used to evaluate backlight, bright field and dark field illumination on their ability to minimize variations within a pass (clip present) or fail (clip absent) sample set, as well as maximize the separation between sample sets. Results showed that there were clear differences in performance with the different lighting geometries, with over a 30% change in performance. Although it is widely acknowledged that the choice of lighting is not a trivial exercise for machine vision systems, this paper provides a case study of the quantitative performance of different lighting geometries.

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.

Contrast Asynchronies

2017 ◽  
Author(s):  
Arthur G. Shapiro
Keyword(s):  
Visual System ◽  
Dark Field ◽  
The Other ◽  
Color Contrast ◽  
Visual Responses ◽  
Bright Field ◽  
Actual Effect ◽  
Different Types ◽  
Contrast Information ◽  
Basic Configuration

Contrast asynchronies juxtapose color and color contrast information. The basic configuration of a contrast asynchrony consists of two identical disks whose luminance levels change in time from light to dark and back again; one disk is surrounded by a bright field and the other by a dark field; at 1Hz, observers report seeing the disks modulating in antiphase, yet also becoming light and dark at the same time. While such a configuration may look like a dynamic brightness illusion, the actual effect occurs because the visual system separates the in-phase luminance information from the antiphase contrast information. Variations of the contrast asynchrony paradigm can isolate different types of visual responses information.

Upgrading Standard Bright-Field Microscopes for Dark-Field and Phase Contrast

2012 ◽  
Vol 21 (1) ◽  
pp. 10-16 ◽  
Author(s):  
Jörg Piper
Keyword(s):  
Focal Plane ◽  
Phase Contrast ◽  
Standard Technique ◽  
Living Cells ◽  
Dark Field ◽  
Transmitted Light ◽  
The Other ◽  
Low Density ◽  
Bright Field ◽  
Blood Smears

Bright-field illumination is widely used as standard technique for examination of transparent specimens characterized by an appropriate optical density so that the transmitted light is partially absorbed when passing the specimens (for example, stained histological sections and blood smears). On the other hand, thin and colorless low-density specimens, such as unstained living cells that do not reduce the amplitude of the transmitted light, cannot be well perceived in bright field because of their ultra-low natural contrast. These so-called phase specimens can be examined when an apparatus for phase contrast is used. Phase contrast can be carried out with special objectives fitted with a phase ring situated within or near their back focal plane. Moreover, the condenser must be fitted with annular light masks (light annuli) that are projected onto the plane of the objective's phase ring so that both components, light annuli and phase rings, are optically congruent and conjugate.

Some characteristics of edge fringes in diffraction contrast images of grain boundaries

1992 ◽  
Vol 50 (2) ◽  
pp. 1454-1455
Author(s):  
S. C. Cheng ◽  
S. S. Sheinin
Keyword(s):  
Grain Boundaries ◽  
Dark Field ◽  
The Other ◽  
Bright Field ◽  
General Properties ◽  
Diffraction Contrast

The methods used to characterize interfaces from diffraction contrast images are normally based on the contrast exhibited by the edge fringes in these images. In one approach to this problem, Amelinckx et al. have characterized the edge fringes due to a displacement at an interface as being α fringes and the edge fringes which are due to a difference in orientation across the boundary as being δ fringes. The general properties of so called symmetrical δ fringes can be summarized as follows: bright field images are asymmetrical (i.e. one edge fringe is dark while the other is bright) while dark field fringes are symmetrical. Of particular interest in the generation of δ fringes are situations in which the reflections, g and h in Fig. 1b (and therefore 0 and g - h in the same figure) are very close. Under these circumstances both bright and dark field images will be formed with two reflections (either 0 and g-h or g and h) passing through the objective aperture.

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