Visualization of latent fingerprints using fluorescence lifetime imaging on paper emitting strong fluorescence.

Latent fingerprints were successfully visualized using fluorescence lifetime imaging (FLIM) on paper which emits strong fluorescence with a lifetime close to that of fingerprints and thus from which it is difficult for time-resolved spectroscopy to visualize fingerprints. Latent fingerprint samples on paper were excited using a 450 nm or 532 nm nanosecond pulsed-laser, and time-resolved fluorescence images were obtained at a delay time of 6-16 ns in intervals of 1 ns, to the excitation pulse. The excitation beam was expanded using a lens, and the fluorescence from the fingerprints was captured using an intensified CCD camera.

Application of mist to fingermark detection: Misting with high-boiling-point liquid containing p-dimethylaminocinnamaldehyde and cyanoacrylate.

In order to detect latent fingerprints that could be damaged by liquid or powder reagents, non-destructive processes such as gaseous reagents have been developed. In this report, we propose the use of fine mist generated when hot vapor of high-boiling-point liquids is rapidly cooled by surrounding air for fingermark detection. Octyl acetate (OA), 2-phenoxyethanol (2PE), and methyl decanoate (MD) were found to efficiently produce mist when heated to 230°C.

Independent component analysis of hyperspectral data measured from overlapping latent fingermarks: Forensic potential of independent component images.

Overlapping fingermark images are sometimes discarded because fingermark collation for the individual fingermarks is difficult. Fluorescence hyperspectral data (HSD) measured using the models of double overlapping fingermarks obtained under the excitation of a high-power, continuous wave, green laser is suitable for obtaining individual fingermark images. However, there are limitations such as the problems on each spectrum of the individual fingermark and the forensic value of the obtained images.

Separation of overlapping fingerprints by principal component analysis and multivariate curve resolution-alternating least squares analysis of hyperspectral imaging data.

Overlapping fingerprints are often found at crime scenes, but only individual fingerprints separated from each other are admissible as evidence in court. Fingerprint components differ slightly among individuals, and thus their fluorescence spectra also differ from each other. Therefore, the separation of overlapping fingerprints using the difference of the fluorescence spectrum was performed with a hyperspectral imager.

Differentiation of black writing ink on paper using luminescence lifetime by time-resolved luminescence spectroscopy.

The time-resolved luminescence spectra and the lifetimes of eighteen black writing inks were measured to differentiate pen ink on altered documents. The spectra and lifetimes depended on the samples. About half of the samples only exhibited short-lived luminescence components on the nanosecond time scale.

Visualization of Aged Fingerprints with an Ultraviolet Laser.

Detection of aged fingerprints is difficult because they can degrade over time with exposure to light, moisture, and temperature. In this study, aging fingerprints were visualized by time-resolved spectroscopy with an ultraviolet-pulsed laser. Fingerprints were prepared on glass slides and paper and then stored under three lighting conditions and two humidity conditions for up to a year.

Portable hyperspectral imager with continuous wave green laser for identification and detection of untreated latent fingerprints on walls.

Untreated latent fingerprints are known to exhibit fluorescence under UV laser excitation. Previously, the hyperspectral imager (HSI) has been primarily evaluated in terms of its potential to enhance the sensitivity of latent fingerprint detection following treatment by conventional chemical methods in the forensic science field. In this study however, the potential usability of the HSI for the visualization and detection of untreated latent fingerprints by measuring their inherent fluorescence under continuous wave (CW) visible laser excitation was examined.

Visualizing latent fingerprints on color-printed papers using ultraviolet fluorescence.

Laser detection of latent fingerprints on a white paper has been performed, previously. Ultraviolet fluorescence from various kinds of printer toner and ink used for home printers were measured to study fluorescence imaging of fingerprints on a color-printed white paper. The experimental system consisted of a nanosecond pulsed tunable laser and a cooled CCD camera.

Individual camera identification using correlation of fixed pattern noise in image sensors.

This paper presents results of experiments related to individual video camera identification using a correlation coefficient of fixed pattern noise (FPN) in image sensors. Five color charge-coupled device (CCD) modules of the same brand were examined. Images were captured using a 12-bit monochrome video capture board and stored in a personal computer.

Fluorescence spectra and images of latent fingerprints excited with a tunable laser in the ultraviolet region.

Fluorescence spectra of sebum-rich latent fingerprints were studied with a tunable laser for non-destructive fingerprint detection without chemical treatment. The tunable laser consists of a nanosecond pulsed Nd-YAG laser and an optical parametric oscillator (OPO) crystal. The fluorescence spectra and images were measured at various excitation wavelengths in the ultraviolet region by the time-resolved fluorescence method.

Ultraviolet fluorescence imaging of fingerprints.

We studied fluorescence imaging of fingerprints on a high-grade white paper in the deep ultraviolet (UV) region with a nanosecond-pulsed Nd-YAG laser system that consists of a tunable laser and a cooled CCD camera. Clear fluorescence images were obtained by time-resolved imaging with a 255- to 425-nm band-pass filter, which cuts off strong fluorescence of papers. Although fluorescence can be imaged with any excitation wavelength between 220 and 290 nm, 230 and 280 nm are the best in terms of image quality.

Ultraviolet fluorescence spectra of fingerprints.

We have studied inherent fluorescence spectra and imaging of fingerprints in the deep ultraviolet (UV) region with a nanosecond-pulsed Nd-YAG laser system that consists of a tunable laser, a cooled CCD camera, and a grating spectrometer. In this paper, we have studied UV fluorescence spectra of fingerprints under 266-nm illumination. Fluorescence spectra of fingerprints have two main peaks, around 330 nm (peak A) and 440 nm (peak B).