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.

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.

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.

scholarly journals On machine vision and photographic imagination

AI & Society ◽  
2020 ◽  
Author(s):  
Daniel Chávez Heras ◽  
Tobias Blanke
Keyword(s):  
Computer Vision ◽  
Deep Learning ◽  
Machine Vision ◽  
Vision Systems ◽  
Computational Aesthetics ◽  
Television Programme ◽  
Computer Vision Systems ◽  
Learning Machine

Abstract In this article we introduce the concept of implied optical perspective in deep learning computer vision systems. Taking the BBC's experimental television programme “Made by Machine: When AI met the Archive” (2018) as a case study, we trace a conceptual and material link between the system used to automatically “watch” the television archive and a specific type of photographic practice. From a computational aesthetics perspective, we show how deep learning machine vision relies on photography, its technical regimes and epistemic advantages, and we propose a novel way to identify the latent camera through which the BBC archive was seen by machine.

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).

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.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

Imaging of platinum-shadowed macromolecular complexes in dark field

1984 ◽  
Vol 42 ◽  
pp. 146-147
Author(s):  
D.W. Andrews ◽  
F.P. Ottensmeyer
Keyword(s):  
Thin Film ◽  
Three Dimensional ◽  
Average Diameter ◽  
Dark Field ◽  
Bright Field ◽  
Field Mode ◽  
Macromolecular Complexes ◽  
Average Mass ◽  
Topological Features ◽  
Projection Images

Shadowing with heavy metals has been used for many years to enhance the topological features of biological macromolecular complexes. The three dimensional features present in directionaly shadowed specimens often simplifies interpretation of projection images provided by other techniques. One difficulty with the method is the relatively large amount of metal used to achieve sufficient contrast in bright field images. Thick shadow films are undesirable because they decrease resolution due to an increased tendency for microcrystalline aggregates to form, because decoration artefacts become more severe and increased cap thickness makes estimation of dimensions more uncertain.The large increase in contrast provided by the dark field mode of imaging allows the use of shadow replicas with a much lower average mass thickness. To form the images in Fig. 1, latex spheres of 0.087 μ average diameter were unidirectionally shadowed with platinum carbon (Pt-C) and a thin film of carbon was indirectly evaporated on the specimen as a support.

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