A theoretical and experimental study of the imaging of latent fingerprints by a phase-resolved fluorescence technique along with associated signal-processing analysis is described. The system configuration is optimized by incorporation of a novel approach of homodyne-assisted even-step phase shifting in a signal-processing concept. The excitation laser source and gain of the detection device, which are modulated at megahertz frequency followed by sensitive signal-processing concepts, are employed to separate the fingerprint fluorescence from background fluorescence. Experiments are carried out with fingerprints deposited upon different types of substrate surfaces. Later, a quantitative image-quality assessment is carried out, which confirms the improvement in the quality of the phase-resolved fingerprint image. Imaging of older fingerprints with better contrast is also carried out with the proposed novel technique.
© 2005 Optical Society of America
(070.6020) Fourier optics and signal processing : Continuous optical signal processing
(110.3000) Imaging systems : Image quality assessment
(120.2920) Instrumentation, measurement, and metrology : Homodyning
(300.2530) Spectroscopy : Fluorescence, laser-induced
U. S. Dinish, Z. X. Chao, L. K. Seah, A. Singh, and V. M. Murukeshan, "Formulation and implementation of a phase-resolved fluorescence technique for latent-fingerprint imaging: theoretical and experimental analysis," Appl. Opt. 44, 297-304 (2005)