This study helps to determine the optimum excitation wavelengths for the fingerprint samples treated with above-mentioned magnetic powders. Treated fingerprints on non-fluorescing PMMA substrates were used for the examina-tion.
The experimental setup is as shown in Fig. 1. The samples were placed in the sample chamber and light from the broadband light source (Poly light, Omnichrome Spec-trum 9000) was used to excite the sample through a liquid light guide. The bandwidth (intensity) of spectral line and the excitation angle, ‘u’, were kept constant at 70 nm and 208, respectively, while the excitation wavelengths were scanned from 300 nm to 550 nm. The fluorescence signals, which are collected using an optical fiber is then fed to the spectrometer (Avantes, AVS-2000) that utilizes a 2048-ele-ment linear array detector, charged-coupled device (CCD). The results were then displayed using the ‘Avasoft’ data acquisition software, via the ADC-1000-USB interface. Wavelength of the excitation source is increased in steps of 5 nm and the corresponding fluorescence emission inten-sity was noted and then plotted against the corresponding excitation wavelength.