We present an analysis and demonstration of using laser-speckle contrast imaging (LSCI) as a sensing modality for presentation attack detection in biometric authentication systems. We provide the design of an experimental testbed for the quantitative characterization of LSCI and measurement results for optimization of the parameters of the active imaging testbed. LSCI has traditionally been used as a qualitative tool for identification of blood flow in dermal micro-vasculature for diagnosis of tissue health. We have built a laboratory phantom model, simulating blood flow beneath diffuse tissue to enable quantitative characterization of the performance of LSCI as a function of both target and imaging system parameters. Our first testbed configuration was an objective LSCI setup, detecting unfocused light on a focal plane array. In objective configuration, we characterized speckle size and speckle contrast as a function of the testbed parameters. In the second testbed configuration, we evaluated the performance of objective LSCI for complex fluid flow scenes. Finally, we report on the quantitative measurement of speckle contrast as a function of fluid flow rate, thereby demonstrating the use of optimized LSCI as an important sensing modality for the detection of presentation attacks in biometric authentication systems.
This paper discusses the effect of periodic roughness and surface defects on the electromagnetic scattering of
terahertz waves from cylindrical objects. The cylinders, possessing periodic roughness imparted during their fabrication
process, had average roughness values ranging from approximately 0.1 μm - 0.50 μm. Metallic cylinders were
fabricated from lathe-turned aluminum rods and dielectric cylinders were fabricated using a rapid prototype technique
(stereolithography). The scattering behavior of the rough cylinders was measured in 160 GHz and 350 GHz compact
radar ranges. In addition, the effect of seams and grooves on the scattering behavior of cylinders will also be presented.