Correlation of topography measurements of NIST SRM 2460 standard bullets by four techniques

Abstract

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 CCFmax. If the compared signatures were exactly the same, CCFmax would be 100%. Comparison results show close agreement among the four techniques for bullet profile signature measurements. The average CCFmax 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.

Calibration and verification of areal surface texture measuring instruments

“…This electromagnetic surface, as it is called in the ISO standards, will vary from optical instrument to optical instrument, although there are many common underlying features of optical instruments [25], and may or may not be significantly different from the mechanical surface. Ideally, under carefully controlled conditions of measurement and filtering, the topography of the optical surface may not be significantly different from that of the mechanical surface [161].…”

On the Relationship Between Deformation-Induced Surface Roughness and Plastic Strain in AA5052—Is it Really Linear?

“…This protocol has been shown to effectively remove long wavelength two-dimensional distortions from three-dimensional data with minimum influence on the magnitude of the short wavelength (roughness) components. [26] After a series of parametric evaluations, we achieved the most effective filtering with a filter mask of 107.8 lm and a long wavelength cutoff of 34.4 lm. The change in the shape of the PDFs in Figure 4(c) shown before and after the application of the PCG filter demonstrates that the application of this high-pass filter considerably reduced the influence of the distortion.…”

Identifying Diagonal Cutter Marks on Thin Wires Using 3D Imaging

“…Several 3D imaging methods, for example scanning white light interferometry (SWLI), confocal microscopy (CM), conoscopic holography, and dynamic focusing techniques, have been applied in forensic work , to make comparing samples more efficient than what is currently possible with 2D imaging. Recent articles present CM and SWLI as suitable measurement methods for forensic 3D imaging of toolmarks on metal samples. Although cm‐size samples have been studied extensively and although 3D methods have potential to be used on smaller marks , only few results on cutter marks on thin wires have been published.…”