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1993

Iowa State University

Semiconductor and Optical Materials

Articles 1 - 14 of 14

Full-Text Articles in Physics

Application Of Diffracto Sight Ot The Nondestructive Inspection Of Aircraft Structures, Jerzy Komorowski, Ronald W. Gould, David L. Simpson, Omer Hageniers Jan 1993

Application Of Diffracto Sight Ot The Nondestructive Inspection Of Aircraft Structures, Jerzy Komorowski, Ronald W. Gould, David L. Simpson, Omer Hageniers

Review of Progress in Quantitative Nondestructive Evaluation

The D Sight optical set up was first assembled nearly ten years ago at Diffracto Ltd. It has received several patents, the first of which was in the United States [1]. Since the mid 1980’s, D Sight has been successfully applied to surface quality inspections, particularly in the automotive and plastics industries. Recently, Komorowski et al. [2–5] have shown several potential applications of D Sight in the field of nondestructive inspection of aircraft structures. The technique has been shown to be particularly effective in locating nonvisible impact damage on large surfaces of aircraft structures built from composite materials ...


High-Speed Time-Resolved Holography For Imaging Transient Events, Michael Ehrlich, James W. Wagner Jan 1993

High-Speed Time-Resolved Holography For Imaging Transient Events, Michael Ehrlich, James W. Wagner

Review of Progress in Quantitative Nondestructive Evaluation

A time-resolved holographic system was developed to study detonation dynamics in dispersed solid particulate explosives. This required a system capable of recording a rapid sequence of exposures during the approximate 1/µs lifetime of the detonation event.


General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart Jan 1993

General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart

Review of Progress in Quantitative Nondestructive Evaluation

This paper presents an approach to automated flaw detection (AFD) in an arbitrary X-ray image. The intensities in the digitized radiographic image are modeled as piecewise-smooth surface functions corrupted by noise and flaws. It has been observed that radiographs generated for NDE purposes containing flaws also have a combination of three unwanted features; background trends, geometrical structures, and noise. These features inhibit the performance of automated flaw detection algorithms. The proposed general processing scheme reduces the unwanted features in such a way that candidate flaws within the image can be identified. The proposed scheme is robust and is applicable to ...


Electronic Holography And Shearography Nde For Inspection Of Modern Materials And Structures, J. Clarady, M. Summers Jan 1993

Electronic Holography And Shearography Nde For Inspection Of Modern Materials And Structures, J. Clarady, M. Summers

Review of Progress in Quantitative Nondestructive Evaluation

Coherent optical techniques such as holography, shearography, and ESPI have been available for inspection applications for years. However, they are still not well known or widely used. In fact, they have sometimes been described as “a solution looking for a problem” and like so many new technologies, they may have been somewhat oversold. These optical NDE methods do, however, offer some impressive advantages over more conventional inspection techniques for the right applications. It is the intent of this paper to provide some basic information on how two of these optical methods, holography and shearography, work discuss capabilities and limitations of ...


Beam Profile Reflectometry: A New Technique For Thin Film Measurements, J. Fanton, J. Opsal, D. L. Willenborg, S. M. Kelso, Allan Rosencwaig Jan 1993

Beam Profile Reflectometry: A New Technique For Thin Film Measurements, J. Fanton, J. Opsal, D. L. Willenborg, S. M. Kelso, Allan Rosencwaig

Review of Progress in Quantitative Nondestructive Evaluation

In the manufacture of semiconductor devices, it is of critical importance to know the thickness and material properties of various dielectric and semiconducting thin films. Although there are many techniques for measuring these films, the most commonly used are reflection spectrophotometry [1,2] and ellipsometry [3]. In the former method, the normal- incidence reflectivity is measured as a function of wavelength. The shape of the reflectivity spectrum is then analyzed using the Fresnel equations to determine the thickness of the film. In some cases, the refractive index can also be determined provided that the dispersion of the optical constants are ...


Electronic Shearography: Current Capabilities, Potential Limitations, And Future Possibilities For Industrial Nondestructive Inspection, John Deaton Jr., Robert S. Rogowski Jan 1993

Electronic Shearography: Current Capabilities, Potential Limitations, And Future Possibilities For Industrial Nondestructive Inspection, John Deaton Jr., Robert S. Rogowski

Review of Progress in Quantitative Nondestructive Evaluation

Image-shearing speckle pattern interferometry, more commonly referred to as ‘shearography’, is a full-field, laser-based interferometric technique first developed for applications in experimental mechanics [1,2]. Shearography is sensitive to derivatives of the out-of-plane surface displacement of a body under load, as opposed to other full-field methods such as holographic interferometry and conventional speckle pattern interferometry, which typically contour the surface displacement directly [3]. The early shearography experiments used high-resolution photographic film to record images of the laser speckle patterns. In contrast to traditional film-based techniques, electronic shearography uses an electronic camera for image recording [4]. This technology, commercially available for ...


Quantitative Analysis Of A Class Of Subsurface Cracks Using Shearography And Finite Element Modeling, Leland Melvin, Brooks A. Childers, James P. Fulton Jan 1993

Quantitative Analysis Of A Class Of Subsurface Cracks Using Shearography And Finite Element Modeling, Leland Melvin, Brooks A. Childers, James P. Fulton

Review of Progress in Quantitative Nondestructive Evaluation

The application of a full field non-contacting measurement system for nondestructively evaluating (NDE) subsurface flaws in structures has been conducted using Electronic Shearography. Shearography has primarily been used as a qualitative tool for locating areas of stress concentration caused by anomalies in materials[1–4]. NASA has been applying optical techniques such as these to NDE inspection of aircraft lap joint integrity, composite material defects, and pressure vessel quality assurance. This paper examines a special class of defects manufactured in thin metal panels and serves as a testbed for interpreting the displacement gradients produced on a simple well-characterized sample with ...


Laser Shearographic Testing Of Foam Insulation On Cryogenic Fuel Tanks, Douglas Burleigh, James E. Engel, David R. Kuhns Jan 1993

Laser Shearographic Testing Of Foam Insulation On Cryogenic Fuel Tanks, Douglas Burleigh, James E. Engel, David R. Kuhns

Review of Progress in Quantitative Nondestructive Evaluation

The Centaur is a high-energy rocket used as a second stage to the Atlas launch vehicle. The Centaur is cryogenically fueled, using liquid hydrogen and liquid oxygen, and requires insulation to prevent fuel boiloff prior to launch. The original insulation system used on Centaur is a set of fiberglass honeycomb panels, which are jettisoned after launch. These panels are still used on the Atlas I version of Atlas/Centaur.


Shearography With Syncrhonized Pressure Stressing, Tom Chatters, Bruno Pouet, Sridhar Krishnaswamy Jan 1993

Shearography With Syncrhonized Pressure Stressing, Tom Chatters, Bruno Pouet, Sridhar Krishnaswamy

Review of Progress in Quantitative Nondestructive Evaluation

Non-destructive evaluation (NDE) techniques of optical video-based speckle interferometry are gaining importance as inspection tools, particularly by the aerospace industry [1,2]. An optical technique such as shearography is attractive to the NDE community largely because of its non-contacting nature, full-field measurement and fast inspection results. However, in order for this optical interferometric method to become widely used as an NDE tool, this technique must be made to be robust enough to operate in noisy environments typically found in industry settings. In this paper, we address these issues for the case of detection of disbonds using shearography in conjunction with ...


Practical Estimates Of The Errors Associated With The Governing Shearography Equation, John Fulton, M. Namkung, L. D. Melvin Jan 1993

Practical Estimates Of The Errors Associated With The Governing Shearography Equation, John Fulton, M. Namkung, L. D. Melvin

Review of Progress in Quantitative Nondestructive Evaluation

In a series of papers Hung[1–3] pioneered the development of shearography, an optical NDE technique that detects gradients of surface displacements. Its utility for qualitative flaw characterization has been demonstrated, and while there is a need for using shearography in NDE for quantitative analysis, a large amount of the research[2–7] has concentrated on the qualitative evaluation of structures and materials. The purpose of this paper is to begin building upon a foundation for the newly emerging quantitative shearography[8].


Noise Reduction Techniques For Electronic Speckle Interferometry, Bruno Pouet, Sridhar Krishnaswamy Jan 1993

Noise Reduction Techniques For Electronic Speckle Interferometry, Bruno Pouet, Sridhar Krishnaswamy

Review of Progress in Quantitative Nondestructive Evaluation

Video-based speckle interferometric methods such as electronic speckle pattern interferometry (ESPI) allow us to measure full-field surface deformation of a diffuse object. In this paper we show, in a first step, that the susceptibility of ESPI to noise can be substantially reduced [1] by synchronizing the optical interferometer and the object stressing system with the CCD image acquisition and processing system, and by performing what amounts to a repetitive sequence of rapid ESPI tests. In this manner, a stable fringe pattern can be obtained as long as the ambient noise is of sufficiently lower frequency than the video acquisition rate ...


"Vision" Approach Of Calibration Methods For Radiographic Systems, Christophe Icord, Philippe Rizo, Pascal Sire Jan 1993

"Vision" Approach Of Calibration Methods For Radiographic Systems, Christophe Icord, Philippe Rizo, Pascal Sire

Review of Progress in Quantitative Nondestructive Evaluation

The geometric calibration of radiographic systems cannot be avoided in image reconstruction problems in stereoradiography, X-ray or SPECT tomography. This operation performed usually before the object examination, provides the relative positions of the different parts of the system (object, source, detector). The source-detector geometry is then described by intrinsic parameters, and the scanning motion by extrinsic ones.


Measured Effects Of Surface Cloth Impressions On Polar Backscatter And Comparison With A Reflection Grating Model, Eric I. Madaras, Edwin F. Brush Iii, S. Lori Bridal, Mark R. Holland, J. G. Miller Jan 1993

Measured Effects Of Surface Cloth Impressions On Polar Backscatter And Comparison With A Reflection Grating Model, Eric I. Madaras, Edwin F. Brush Iii, S. Lori Bridal, Mark R. Holland, J. G. Miller

Review of Progress in Quantitative Nondestructive Evaluation

Integrated polar backscatter has been shown to have potential applications to composites, especially for the detection of matrix cracking, delaminations, fiber waviness, fiber fracture, inclusions and porosity [1–11]. The method was attractive because it avoided several measurement limitations inherent to conventional pulse echo techniques. Polar backscatter, however, has not been without its disadvantages. It has been reported that surface texture introduces unwanted artifacts in images made using the polar backscatter method [12]. One suggested method to overcome this limitation was the use of stripable coatings, which are paints that approximately match the impedance of the composite surface and have ...


Light Scatterometry As An Nde Technique For Surface Characterization Of Ge Windows, I. Perez, M. Wilson, M. Thomas, D. Price, W. R. Scott Jan 1993

Light Scatterometry As An Nde Technique For Surface Characterization Of Ge Windows, I. Perez, M. Wilson, M. Thomas, D. Price, W. R. Scott

Review of Progress in Quantitative Nondestructive Evaluation

Germanium is a material with optimal infrared (IR) transmission properties but poor mechanical properties[1]. As a result, repeated water drop impacts on polished Ge windows with velocities greater than 170 m/s produce considerable amounts of surface and subsurface damage (see Figure 1). This results in IR transmission loss through these windows[2]. The mechanics of the water drop/solid surface interaction has been amply described in the literature[3] and will not be discussed here. In order to maintain optimum IR system performance, one needs to monitor the damage evolution on these windows. The technique required should be ...