Fingerprints provide important clues to criminal investigations. Although there are various fingerprint detection methods such as powder or liquid, optical methods are useful for non-contact and non-destructive detection. However, in case of two or more overlapping fingerprints, they might be discarded because the features cannot be assigned to the individual fingerprints. The fact that the composition of fingerprints is unique for each individual is well known, so if this causes differences in inherent emission spectra of fingerprints, it is possible to separate overlapping fingerprints. Hyperspectral imaging is used in a variety of fields and also in forensic science, such as fingerprint detection. In this study, the separation of overlapping fingerprints using multivariate analysis was performed for effective use of fingerprints. Fluorescence hyperspectral data of overlapping fingerprints excited by a 532 nm CW laser were acquired by hyperspectral imaging in the visible region. Fluorescence spectra from fingerprints were measured in the wavelength range from 560 to 700 nm with the wavelength resolution of 1.1 nm. Thus, the hyperspectral data cube consisted of 600 (image) × 960 (image) × 128 (wavelength) pixels. An image, which are integrated over the wavelength range, showed the two fingerprints overlapping each other. Separation of overlapping fingerprints was tried applying principal component analysis, multivariate curve resolution - alternating least squares analysis, and partial least squares analysis to the fluorescence hyperspectral data. Among three methods examined herein, partial least squares analysis was found to be most effective for fingerprint separation.
Image enhancement of pre-processed and colored fingerprints such as ninhydrin-processed fingerprints in a complexpatterned background is important in crime investigation. Contrast adjustment, which is one of the most common image processing methods usually has a limitation in enhancing such fingerprints because of interference superposing patterns of the background. We propose three image processing methods using color information or spatial frequency information of an RGB material image. The first method is a hue-based method, which converts hue values of each pixel in CIELAB color space to corresponding brightness. The second method is a PCA-based method, which conducts principal component analysis on a color data of the material image and reconstructs three principal component images. Both proposed methods achieve more enhanced fingerprint images than the contrast adjustment gives. The PCA-based method works well even when the hue-based method does not. As the third proposed method, remaining background periodic patterns are removed for fingerprint enhancement by spatial frequency filtering using the Fast Fourier Transformation. According to estimated frequency components of background periodic patterns, we altered the width of frequency removing region of such background patterns, suggesting that there is an optimal width for each material for fingerprint enhancement. Also, we tested four different edge profiles of the frequency removing region and checked that an edge profile with gradual change tends to reduce the effect of suppressing the background periodic patterns compared to an edge profile with sharp change under the equivalent width of removing region of frequency components.
We applied a wide-field time-resolved luminescence (TRL) method with a pulsed laser and a gated intensified charge coupled device (ICCD) for deciphering obliterated documents for use in forensic science. The TRL method can nondestructively measure the dynamics of luminescence, including fluorescence and phosphorescence lifetimes, which prove to be useful parameters for image detection. First, we measured the TRL spectra of four brands of black porous-tip pen inks on paper to estimate their luminescence lifetimes. Next, we acquired the TRL images of 12 obliterated documents at various delay times and gate times of the ICCD. The obliterated contents were revealed in the TRL images because of the difference in the luminescence lifetimes of the inks. This method requires no pretreatment, is nondestructive, and has the advantage of wide-field imaging, which makes it is easy to control the gate timing. This demonstration proves that TRL imaging and spectroscopy are powerful tools for forensic document examination.
Actual case examples and further improvements on source camera identification are shown. There are three specific topics in this paper: (a) In order to improve performance of source camera identification, the hybrid identification scheme using both dark current non-uniformity (DCNU) and photo-response non-uniformity (PRNU) is proposed. The experimental results indicated that identification performance would be improved by properly taking advantage of their features; (b) Source camera identification using non-uniform nature of the CCD charge transfer circuit is proposed. The experimental results with twenty CCD modules of the same model showed that individual camera identification for dark images was possible by the proposed method. Furthermore, it was shown that the proposed method had higher discrimination capability than the method using pixel non-uniformity when the number of recorded image was small; (c) The authors have been performed source camera identification in the five actual criminal cases, such as homicide case, and so on. The analytical procedure was a sequential examination of hot pixel coordinates validation followed by the similarity evaluation of sensor noise pattern. The authors could clearly prove that the questioned criminal scenes had been recorded by the questioned cameras in four cases of the five.
Radiation-induced malfunction and degradation of electronic modules in certain operating
conditions are described in this report. The cumulative radiation effects on Atmel AVR
microcontrollers, and 2.4 GHz and 303 MHz wireless network devices were evaluated under
gamma ray irradiation with dose rates of 100, 10 and 3 Gy/h. The radiation-induced
malfunctions occurred at doses of 510±22 Gy for AVR microcontrollers, and 484±111 and
429±14 Gy for 2.4 GHz and 303 MHz wireless network devices, respectively, under a 100 Gy/h
equivalent dose rate. The degradation of microcontrollers occurred for total ionizing doses
between 400 and 600 Gy under X-ray irradiation. In addition, we evaluated the reliability of
neutron dosimeters using a standard neutron field. One of the neutron dosimeters gave a reading
that was half of the standard field value.
We have reported the Charge Coupled Device (CCD) fingerprint method for identification of digital still cameras. The CCD fingerprint method utilizes the nonhomogeneous nature of dark currents in CCDs. In this study, we have measured CCD defects patterns of various digital still cameras including professional cameras and cheap ones with various resolution and compression rates. As a result, CCD defect pattern was detected in all cameras except for a low-resolution cheap camera using only one image. Resolution mode change of digital cameras did not affect the position of defect points in general but in some cases, relative pixel intensity varied. Image compression did not affect the pixel position for blank images within normal compression rate, but when there existed light in the background, the pixel position was blurred as the compression rate became high. In conclusion, it is recognized that the CCD fingerprint method can be applied in principle to digital still cameras, that is, individual camera identification can be achieved in principle by using images taken with the camera.
The purpose of this study is visualization of concealed light elements materials in metallic environments using a cooled CCD camera with an image intensifier. In this study, gamma-rays were used for visualization. As a gamma-ray source, radio-isotopes such as 57Co, 133Ba and 137Cs were used. Gamma-rays penetrate through sample materials and are firstly enhanced by an image intensifier and then detected by a cooled CCD camera. Materials such as explosives or organic matters were observed through various metal plates.
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