BallisticSEM For examination and comparison of ballistic evidence in the SEM
Comparisons of bullets, cartridge cases or other cylindrical items are commonly performed in the optical comparison microscope. In some cases, however, it may be advantageous to examine the same materials in a scanning electron microscope. The images from such samples taken in an SEM show very different characteristics compared with those obtained by optical microscopy. Electron microscopic images can show details of the surface chemistry of the ballistic materials and contaminants adhering to them. These features can be observed using the backscattered electron signal in the SEM or be chemically analyzed using the SEM’s EDS X-ray analyzer. BallisticSEM permits microscopists to conveniently image the surfaces of bullets and cartridge cases. The system allows manipulation of two bullets or cartridge cases in a similar way to the stages provided with optical comparison microscopes. Both samples can be rotated continuously and independently in the SEM vacuum.
The BallisticSEM system software enables the convenient and efficient comparison of images of two samples or comparison with library images. The software rapidly acquires the images of samples using either the SE, BSE or optical images. These can be obtained from an external optical microscope or from an optional in-column boroscope optical imaging system (can be provided EA). The software can gather images from the SEM’s signal sources (SE and BSE) or via integrated frame grabbers (RS-170 CCTV or IEEE 1384 Firewire DV), or simply from storage over the network.
The two main images can be live simultaneously and can have differently optimized acquisition characteristics (contrast, brightness, and other CODEC parameters) if the installed hardware allows this. The two images can be compared interactively using live overlay, and a combination formed by merging the two images. The result is convenient, direct comparison and documentation of features. The integrated measuring tool provides direct and interactive measurement of distances on sample surfaces. There is also an integrated tool for automatic calibration of SEM magnification. Images can be stored in a wide variety of current as well as older formats. Collections of ballistic images can be compiled into portfolios. The portfolios can contain images from any source, be of any resolution and image file type, and can be at different storage locations (worldwide). The optional Flatview(TM) facility permits the images of curved surfaces to be scanned automatically and compiled into portfolios. Flatview images are images whose Y-axis is a near one-dimensional image slice through the sample, and whose X-axis represents degrees of sample rotation. These images make comparisons of entire cylindrical surfaces simple and convenient.
The Flatview software provides a tool for directly comparing two flat images and for interactive adjustment of relative image positions and rotation phases. Once a match has been reached between two images, a combined image can be formed and saved for later reference.