Time-resolved imaging of latent fingerprints with nanosecond resolution

Imaging of latent fingerprints using time-resolved (TR) method offers a broader platform to eliminate the unwanted background emission. In this paper, a novel TR imaging technique is demonstrated and implemented, which facilitates the detection of latent fingerprints with nanosecond resolution. Simulated experiments were carried out with two overlapping fingerprints treated with two fluorescent powders having different lifetimes in nanosecond range. The dependence of the fluorescence emission intensity in nanosecond resolution of TR imaging is also revealed.     

Double shearography for engineering metrology: optical and digital approach

This paper presents a double shearographic configuration based on the optical method by using two Michelson interferometers in tandem. The problems associated with the extraction of second order derivatives by optical means and a comparison with the proposed novel approach by digital means are discussed in this paper.     

An integrated phase-resolved fluorescence imaging system with sub-nanosecond lifetime resolution

In this paper, a novel configuration of an integrated phase-resolved (PR) fingerprint fluorescence imaging system is proposed and implemented. In this integrated PR imaging system, a current modulated 402 nm dual diode laser is proposed to be the light source, to obtain both high laser power and easy modulability. To estimate the lifetime resolution of this PR imaging system, a novel method of using distance-selective suppression of fluorescence signals from two identical fluorescing samples is proposed. Detailed theoretical and experimental analyses are presented. The experimental results demonstrate that this integrated PR imaging system has a lifetime resolution of 0.1 ns. Fingerprint detection experiments are also carried out using this system with latent fingerprints deposited on substrates of aluminum foil and currency.     

Polarization phase shifting shearography for optical metrological applications

We present here a different and modified configuration in order to obtain the curvature fringes by incorporating phase shifting and image processing techniques. Optical fibers are used for obtaining shear fringes in which we have used Wollaston prism as the shear element.     

Effect of metals on UV-excited plasmonic lithography for sub-50 nm periodic feature fabrication

This paper describes and compares the effect of metal films, such as aluminum (Al) and silver (Ag) on UV-excited two-beam surface plasmon interference nanolithography. A planar four-layer configuration has been employed to study the light intensity distribution on the recording medium. It is observed that high-density sub-50 nm periodic structures were achievable by employing the above-mentioned metal films when interrogated with p-polarized, 364 nm illumination wavelength source. It is found that the obtained periodic feature shows good exposure depth and high contrast when Al is used as a metal film. The initial experimental result of planar four-layer configuration is also presented.     

Periodic patterning using multi-facet prism based laser interference lithography

This paper discusses and present simple wavefront interference concept, using multi facet prisms and UV laser, to pattern periodic micro-features. Fabrication of square lattice features employing a biprism is illustrated. This concept is extended employing three facet prisms to fabricate hexagonal lattice structures. These micro-features are expected to find tunable photonic crystal applications. Original Text ? Astro, Ltd., 2009. The article is published in the original.     

Development of Matlab filtering techniques in digital speckle pattern interferometry

In interferometric fringe pattern analysis, specular and speckle fringe patterns are the two main divisions. While specular fringes are characterized by quality fringes, speckle (that obtains due to the diffuse scattering of the coherent radiation from an optically rough surface) fringe patterns are characterized by noisy fringes. This paper concentrates on this aspect and the Matlab based filtering methods to improve the quality of speckle fringe patterns by developing the appropriate software. Further, the newly developed software “Macurv” will be presented which can give the second order derivative (curvature) fringe information. A software with several functions is written using Matlab. The objective of the software is to provide a more effective way for the post-processing of speckle interferometric fringes. The algorithm and functions of the developed software “Macurv” will be explained.     

Hollow-core photonic crystal fiber based multifunctional optical system for trapping, position sensing, and detection of fluorescent particles

We demonstrate a novel multifunctional optical system that is capable of trapping, imaging, position sensing, and fluorescence detection of micrometer-sized fluorescent test particles using hollow-core photonic crystal fiber (HC-PCF). This multifunctional optical system for trapping, position sensing, and fluorescent detection is designed such that a near-IR laser light is used to create an optical trap across a liquid-filled HC-PCF, and a 473 nm laser is employed as a source for fluorescence excitation. This proposed system and the obtained results are expected to significantly enable an efficient integrated trapping platform employing HC-PCF for diagnostic biomedical applications.     

Digital speckle pattern interferometric (DSPI) and thermo-graphic investigations on the thermal responds in human teeth

Human dentine is a composite material made up of constituents of varying thermal properties, which when subjected to changes in temperature experiences complex thermal effects. In this study, the response of functionally adapted dentine to temperature changes in physiological range is analyzed using a digital speckle pattern interferometer (DSPI) and thermography in conjunction with an advanced digital fringe processing technique. The advanced digital fringe processing is conducted using an asymmetric and central peak Gaussian filter, in order to remove noise and, subsequently, enhance the quality of the images. This investigation demonstrates the responds of functionally adapted dentine to temperature changes in its own plane and out of plane. Distinct pattern of out-of-plane and in-plane displacement was observed on the dentine by the DSPI analysis. The thermo-graphic analysis was used to rationalize the above nature of deformation in the dentine. These analyses showed that the inner, cervical dentine exhibited conspicuous deformation at the maximum temperature rise and equilibrated last during temperature drop.     

Effect of image fiber on the speckle fringe pattern in image fiber-guided DSPI endoscopy

The effect of using an image fiber on the speckle fringe visibility in an endoscopic DSPI is analyzed here. An endoscope system was designed and developed, using image fiber as the speckle pattern image conduit, to work in the out-of-plane speckle interferometric configuration and experiments were carried out using a curved phantom tissue specimen as the test target. Experimental results obtained using the developed system are compared with that obtained using conventional DSPI system. To obtain a relative and quantitative comparison of the quality of the fringes obtained employing the two methods, an evaluation method that can give a quantified ‘score’ is proposed here.