Theodore Vorburger - Academia.edu (original) (raw)

Papers by Theodore Vorburger

Key Engineering Materials, Oct 1, 2005

Autocorrelation and cross-correlation functions are proposed for 2D and 3D surface texture compar... more Autocorrelation and cross-correlation functions are proposed for 2D and 3D surface texture comparisons. At the maximum correlation point of the two correlated surface textures, there is a peak shown at the cross-correlation curve. It is proposed to generate a difference function at the maximum correlation point for evaluation of the difference between the two compared surface textures. Based on this method, the National Institute of Standards and Technology (NIST) bullet signature measurement system is developed for the bullet signature measurements of NIST standard bullets.

Measurement Science Review, 2010

Standard bullets and casings are currently under development to support the National Integrated B... more Standard bullets and casings are currently under development to support the National Integrated Ballistics Information Network (NIBIN) in the U.S. Based on a numerically controlled diamond turning technique, 20 RM 8240 standard bullets were fabricated in 2002. Test results show high repeatability and reproducibility for the bullet signatures on these RM bullets. Prototype standard casings were also manufactured using an electro-forming technique, and are currently under test. These RM bullets and casings are intended for measurement traceability and quality control for ballistics laboratories nationwide.

Journal of Research of the National Institute of Standards and Technology, 2010

Wear, Jun 1, 2011

We describe several examples where we use cross-correlation functions to quantify the similarity ... more We describe several examples where we use cross-correlation functions to quantify the similarity of 2D surface profiles or of 3D areal surface topography images. The applications have included (1) the manufacture of standard reference material (SRM) bullets and casings, (2) methods to assess whether bullets or casings have been fired by the same firearm, and (3) research to quantify similarities or differences between profiles of the same surface measured by different techniques or between a master surface and its replicas. The cross-correlation maximum is the functional parameter used to quantify similarity. A second parameter, called the relative profile (2D) difference or relative areal topography (3D) difference, may also be used to quantify differences and to recognize the ambiguous condition when two results have different vertical (z-) scales but identical shapes. Most of these examples have been applied in support of ballistics inspection methods in crime labs, but the methods are generally useful for estimating the accuracy of surface replication techniques or the ability of different surface topography instruments to measure the same surface and provide the same result. The instruments used in these studies were a stylus instrument and a Nipkow-disk type confocal microscope. Cross-correlation functions may also be used to assess differences resulting from the use of different filters to modify the same surface profile or topography image.

Elsevier eBooks, 2019

Abstract This chapter describes emerging technologies relating to 3D surface topography measureme... more Abstract This chapter describes emerging technologies relating to 3D surface topography measurement and analysis for bullet and cartridge case identification. After a short history of firearm identification systems, we review several types of surface topography measurement systems and image comparison procedures that have been proposed and researched. Error rate issues, physical standards, data formatting standards for interoperability, and virtual comparison microscopy are also discussed. Technology is developing quickly and we hope that the content will provide a roadmap and some important waypoints to this emerging discipline.

Measurement Science and Technology, 2006

Three optical instruments including an interferometric microscope, a Nipkow disc confocal microsc... more Three optical instruments including an interferometric microscope, a Nipkow disc confocal microscope and a laser scanning confocal microscope and a stylus instrument are used for the measurements of bullet profile signatures of a National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2460 standard bullet. The two-dimensional profile signatures are compared with the virtual bullet standard signature established by the same stylus instrument. The bullet signature differences are quantified by the maximum cross-correlation function CCF max. If the compared signatures were exactly the same, CCF max would be 100%. Comparison results show close agreement among the four techniques for bullet profile signature measurements. The average CCF max values are higher than 90%. This supports the possibility of using surface topography techniques for ballistic identifications as an alternative to the current technology based on image comparisons.

Areal Cross Correlation Function, a statistical function of three dimensional surface topography ... more Areal Cross Correlation Function, a statistical function of three dimensional surface topography ANOVA Analysis of Variance ATF Bureau of Alcohol, Tobacco, Firearms, and Explosives BF Breech face CCF Cross Correlation Function, a statistical function of two dimensional surface topography DAS Data Acquisition Station, a component of IBIS (below) EEEL Electronics and Electrical Engineering Laboratory, an organizational unit of NIST FP Firing pin

SPIE Proceedings, 2012

Critical Dimension AFM (CD-AFM) is a widely used reference metrology. To characterize modern semi... more Critical Dimension AFM (CD-AFM) is a widely used reference metrology. To characterize modern semiconductor devices, very small and flexible probes, often 15 nm to 20 nm in diameter, are now frequently used. Several recent publications have reported on uncontrolled and significant probe-to-probe bias variation during linewidth and sidewall angle measurements [1,2]. Results obtained in this work suggest that probe bending can be on the order of several nanometers and thus potentially can explain much of the observed CD-AFM probe-to-probe bias variation. We have developed and experimentally tested one-dimensional (1D) and two-dimensional (2D) models to describe the bending of cylindrical probes. An earlier 1D bending model reported by Watanabe et al. [3] was refined. Contributions from several new phenomena were considered, including: probe misalignment, diameter variation near the carbon nanotube tip (CNT) apex, probe bending before snapping, distributed van der Waals-London force, etc. The methodology for extraction of the Hamaker probe-surface interaction energy from experimental probe bending data was developed. To overcome limitations of the 1D model, a new 2D distributed force (DF) model was developed. Comparison of the new model with the 1D single point force (SPF) model revealed about 27 % difference in probe bending bias between the two. A simple linear relation between biases predicted by the 1D SPF and 2D DF models was found. This finding simplifies use of the advanced 2D DF model of probe bending in various CD-AFM applications. New 2D and three-dimensional (3D) CD-AFM data analysis software is needed to take full advantage of the new bias correction modeling capabilities.

Wear, 2011

Journal of Research of the National Institute of Standards and Technology, 1995

Metrologia, 2006

Calibration services of five countries from the Sistema Interamericano de Metrología (SIM) region... more Calibration services of five countries from the Sistema Interamericano de Metrología (SIM) region are compared through measurements of surface roughness and step height standards. A surface roughness standard with a nominal roughness average (Ra) value of 0.2 µm, a surface roughness standard with a nominal Ra value of 3 µm and a nominal spatial wavelength of 99 µm, and three step height standards with nominal values of 2.55 µm, 0.38 µm and 0.03 µm are compared. Special attention is paid to the influence of the long wavelength cutoff ratio of the measurements. Results are reported for Ra, maximum height of profile Rz, mean width of profile elements RSm, and step height d, depending on the sample measured. The initial reported results show that the laboratories agree on all of the measurements within their stated and published uncertainties. Observations are then discussed about the definition of Rz, the effect of instrument noise on Rz, the different step height parameters d and Pt, differences between the laboratories in reporting Type A statistical uncertainties, the method for calculating the uncertainty of the reference value, and the importance of accounting for correlations between the reference value and individual lab values when calculating the degrees of equivalence. After corrections and reanalysis the laboratories still agree well considering their stated uncertainties.

Measurement Science and Technology, 2005

Line edge roughness (LER) measurements using two types of atomic force microscopes and three type... more Line edge roughness (LER) measurements using two types of atomic force microscopes and three types of tips are compared. Measurements were made on specially prepared samples with inscribed edge roughness of different amplitudes and wavelengths. The spatial wavelengths and amplitudes each instrument was able to measure are compared. Techniques on checking the noise level of LER measuring instruments are highlighted.

Key Engineering Materials, 2005

Scanning Microscopy 2010, 2010

The National Institute of Standards and Technology (NIST), Advanced Surface Microscopy (ASM), and... more The National Institute of Standards and Technology (NIST), Advanced Surface Microscopy (ASM), and the National Metrology Centre (NMC) of the Agency for Science, Technology, and Research (A*STAR) in Singapore have completed a three-way interlaboratory comparison of traceable pitch measurements using atomic force microscopy (AFM). The specimen being used for this comparison is provided by ASM and consists of SiO 2 lines having a 70 nm pitch patterned on a silicon substrate. NIST has a multifaceted program in atomic force microscope (AFM) dimensional metrology. One component of this effort is a custom in-house metrology AFM, called the calibrated AFM (C-AFM). The NIST C-AFM has displacement metrology for all three axes traceable to the 633 nm wavelength of the iodine-stabilized He-Ne laser-a recommended wavelength for realization of the SI (Système International d'Unités, or International System of Units) meter. NIST used the C-AFM to participate in this comparison. ASM used a commercially available AFM with an open-loop scanner, calibrated by a 144 nm pitch transfer standard. In a prior collaboration with Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute, ASM's transfer standard was calibrated using PTB's traceable optical diffractometry instrument. Thus, ASM's measurements are also traceable to the SI meter. NMC/A*STAR used a large scanning range metrological atomic force microscope (LRM-AFM). The LRM-AFM integrates an AFM scanning head into a nano-stage equipped with three built-in He-Ne laser interferometers so that its measurement related to the motion on all three axes is directly traceable to the SI meter. The measurements for this interlaboratory comparison have been completed and the results are in agreement within their expanded uncertainties and at the level of a few parts in 10 4 .

Measurement, 2009

The National Institute of Standards and Technology (NIST) in collaboration with the Bureau of Alc... more The National Institute of Standards and Technology (NIST) in collaboration with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) has developed the Standard Reference Material (SRM) 2460 Bullets and 2461 Casings. NIST has also developed a 2D and 3D Topography Measurement and Correlation System for ballistics signature measurements. This system includes stylus instruments and a confocal microscope for 2D and 3D topography measurements, and a 2D and 3D topography correlation program developed by NIST. NIST and ATF are proposing to establish a National Ballistics Measurement Traceability and Quality System using these materials. In this paper, basic concepts and specific requirements for establishing ballistics measurement traceability are introduced; three key issues are discussed that include: (1) establishing a reference standard; (2) establishing an unbroken chain of calibrations; and (3) evaluating measurement uncertainty for both the geometrical topography measurements and the optical image correlations of the ballistics signatures.