ВОЗМОЖНОСТИ ПРИМЕНЕНИЯ ОПТИЧЕСКОЙ ПРОФИЛОМЕТРИИ ПРИ ПРОИЗВОДСТВЕ КРИМИНАЛИСТИЧЕСКОЙ ЭКСПЕРТИЗЫ

The paper deals with current challenges in improving the technical capabilities of forensicdivisions in ballistic and trace evidence examinations focused on surface morphology. Theproposed combination of equipment and methodology enables the automation of morphology measurement and comparative characterization, and thus contributes to ensuring the quality of forensic examinations.Рассматриваются актуальные вопросы совершенствования технико-криминалистическогообеспечения деятельности экспертных подразделений при производстве судебно-баллистических и трасологических исследований, связанных с изучением морфологииповерхности. Предлагаемый технический комплекс в совокупности с методикойпозволяет автоматизировать процесс измерения и сравнения выявленных особенностейморфологии поверхности, что способствует повышению качества проводимыхэкспертными подразделениями исследований

Обеспечение качества поверхностного слоя изделий с гетерогенными покрытиями при механической обработке

It is shown that when machining products from materials with heterogeneous structure, possibilities of management of a condition of a blanket are significantly limited. As an example of management, cutting processing of products from materials with heterogeneous structure – turning of high-strength flame evaporated coverings is considered. Because for an amorphous component of heterogeneous coverings the lack of deformation hardening is peculiar considerable deformation of the cut-off material is observed at their processing and characteristic shaving is formed. Highintensity thermobaric impact on the processed heterogeneous material leads to partial crystallization in a thin blanket with the high content of an amorphous phase. As a result of researches the criterion which quantitatively estimates the statistics, which complexly characterize uniformity of structure of materials and dispersion of their properties, is offered. The criterion allows defining ability of materials to be exposed to cutting without carrying out long experiments.Показано, что при механической обработке изделий из материалов с гетерогенной структурой возможности управления состоянием поверхностного слоя существенно ограничиваются. В качестве примера управления рассмотрена лезвийная обработка изделий из материалов с гетерогенной структурой – точение высокопрочных покрытий, нанесенных газопламенным напылением. В связи с тем что для аморфной составляющей гетерогенных покрытий свойственно отсутствие деформационного упрочнения, при их обработке наблюдается значительная деформация срезаемого материала и образуется характерная стружка. Высокоинтенсивное термобарическое воздействие на обрабатываемый гетерогенный материал приводит к частичной кристаллизации в тонком поверхностном слое с высоким содержанием аморфной фазы. Предложен критерий, количественно оценивающий статистические показатели, которые комплексно характеризуют однородность структуры материалов, разброс их свойств по величине. Критерий позволяет определить способность материалов подвергаться резанию без проведения длительных экспериментов

Correction of Scanning Steps to Improve Accuracy in Interferometric Profilometer

In scanning interferometry of longitudinal shift, an uncertainty of required phase shift performance leads to a measurement error. Such uncertainty can be caused by external factors (vibrations, air turbulence in measuring area etc.) as well as inaccuracy of the scanning system. The method for calculating the phase shift between interferograms, which allows reducing the measurement error, is proposed. The results of numerical and full scale experiments are presented

Visualization and Measurement of Velocity Fields by Means Optical Discrimination of the Doppler Frequency Shift of the Scattered Light

At Doppler Global Velocimetry (DGV) the frequency of the Doppler shifted light scattered from the fluid has to be determined to obtain the velocity field. Standard DGV is based on the principle of transforming the Doppler shifted frequency into variations of grey levels by means of an Iodine cell, the transmittance of which is frequency dependent. Standard DGV configurations require a second reference camera to monitor the flow field. The major problems of the Standard DGV technique at present are limitations of the velocity resolution at low flow velocities and the influence of multi–particle scattering on the results of the velocity measurements. This paper will discuss different solutions to overcome these problems. First, a method of optical discrimination of the Doppler frequency shift has been realized in an optical Doppler processor (ODP) with coherent feedback. This processor is used as a converter frequency ==> intensity. One implementation of the Optical Doppler Processor consists of a semi–confocal interferometer as wide–band spatial frequency filter with resonant transfer function. The slope of its resonance transfer function is used as frequency discrimination curve. The ODP is included in a feed back loop with the laser. In the German Aerospace Center (DLR) in Göttingen joint experiments on visualization and measurement of velocity fields in gas jets from a test nozzle in the regime of low velocities of a few meters/second have been made utilizing the ODP. A method to eliminate the influence of multi–particle scattering on the result of the measurement of velocity fields based on linear operations with frequency–demodulated images of the flow, formed in various areas of the angular spectrum of the scattered light, is proposed. The registration of the image can be made by only one CCD camera without the need of a second camera for a reference image. Eliminating the influence of multi–particle scattering is subject of an application for an European patent

APPLICATIONS OF OPTICAL PROFILOMETRY IN FORENSIC CRIME SCENE INVESTIGATION

The paper deals with current challenges in improving the technical capabilities of forensicdivisions in ballistic and trace evidence examinations focused on surface morphology. Theproposed combination of equipment and methodology enables the automation of morphology measurement and comparative characterization, and thus contributes to ensuring the quality of forensic examinations