Technology.- Advanced Optoelectronics in Optical Fibre Sensors.- Interferometric Distance Sensors.- Optical Tomography: Techniques and Applications.- Optical Waveguide Refractometers.- Characterization of an Optical Fibre pH Sensor with Methyl Red as Optical Indicator.- Optical Sensors and Microsystems Using Liquid Crystals.- Idium Tin Oxide Films for Optical Sensors.- Optoelectronic Neural Networks.- Complex ABCB-matrices: A general Tool for Analyzing Arbitrary Optical Systems.- Microsystems and Related Technologies.- The Stretch-and-write Technique for Fabrication of Fiber Bragg-grating Arrays.- Applications.- Fluorescence Lifetime-based Sensing for Bioprocess and Biomedical Applications.- A Piezoelectric Biosensor as a Direct Affinity Sensor.- The Complex Phase Tracing Based Shape Evaluation System for Orthopaedic Application.- Optical Fibre Chemical Sensors for Environmental and Medical Applications.- to the Multicomponent Analysis with Arrays of Non-selective Chemical Sensors.- High Sensitivity Trace Gas Monitoring Using Semiconductor Diode Lasers.- Optical Fiber Sensors for the Nuclear Environment.- Crlorinated Hydrocarbons Trace Detection in Water by Sparging and Laser IR Gas Phase Detection.- Hollow Core Fiber Guides As Gas Analysis Cells for Laser Spectroscopy.- Chemiluminescence Imaging of Plant Origin Materials.- Optical Fiber Sensors for the Cultural Heritage.- Fiber Optics Reflectance Spectroscopy: A Non-destructive Technique for the Analysis of Works of Art.- Optical Diagnostic Systems and Sensors to Control Laser Cleaning of Artworks.- Electro-optical Sensors for Mechanical Applications.- Optical Fibres and Their Role in Smart Structures.- All Optical Fiber Ultrasonic Sources for Non Destructive Testing and Clinical Diagnosis.
COMPLEX ABCB-MATRICES: A GENERAL TOOL FOR ANALYZING ARBITRARY OPTICAL SYSTEMS (p. 97-98)
1. INTRODUCTION
In this paper, we describe a novel formulation of light beam propagation through any complex optical system that can be described by an ABCD ray-transfer matrix.1,2 Within the framework of complex ABCD-optical systems, we then present novel speckle methods for analyzing linear and angular velocities and displacements. All methods rely on the dynamics of speckle patterns, produced by scattering of coherent light off solid surfaces undergoing angular and/or translational displacements.
Coherent light scattered off a rough surface produces a granular diffraction pattern some distance away from the object. This pattern is referred to as speckles,3 and originates from elementary interference of the waves emanating from many microscopic areas on the surface within the illuminated region. If the illuminated object is in motion, the resulting speckle pattern also evolves with time, i.e., a dynamical speckle pattern results. The target motion or displacement is usually determined by calculating the space- or time-lagged covariance of the detector currents before and after object displacement: and then determine the position where the peak of the covariance attains its maximum.
We first present the basic properties of the ABCD ray-matrix method,1,2 and summarize raymatrices for Simple optical elements,5 e.g., thin lenses, mirrors, and free-space propagation. Additionally, we present the ray-transfer matrix for a Gaussian shaped aperture.1,2 Thus, armed with matrix elements describing the most common elements in an optical system, the resulting ray-transfer matrix can be obtained for most systems encountered in practice. The resulting raytransfer matrix connects the input ray position and slope with the corresponding output parameters. Rather than dealing with rays, a Gaussian Green's function has been developed,1,2 valid for arbitrary ABCD systems, to reveal the transition of the field in the input plane, through the ABCD-optical system, to the output plane.
Armed with the Green's function that reveals the field in the output plane of an arbitrary ABCD-system, provided the field in the input plane is known, we then present a general equation, valid for arbitrary ABCD-optical systems, for the space-time lagged covariance of photocurrent: The position where the Gaussian-shaped covariance attains its maximum reveals information about target velocity or displacement. We discuss, how, in practice, the target velocity/ displacement is assessed. The theoretical results alluded to above are then applied to a series of novel optical sensor applications, all described by the ABCD kernel.
Two systems for measuring hear velocities, viz. the laser Doppler velocimeter6 and the laser time-of-flight velocimeter,7,8 are presented. A compact system for measuring linear surface velocities is presented, where all passive optical components are replaced with a single holographic optical element.9 Additionally, other novel schemes for further system miniaturization are presented.
We then present a new method for measurement of out-of-plane angular displacement in one or two dimensions.12,13 It is demonstrated that the angular displacement sensor is insensitive to both object shape and target distance, and any transverse or longitudinal movements of the target. It is further shown that the method has a resolution of 0.3 mdeg (5 µrad). A new method for measuring in-plane angular velocities or displacements are then presented.14 Here, we consider off-axis illumination, and it is shown that, for Fourier transform optical systems, in-plane rotation causes the speckles to translate in a direction perpendicular to the direction of surface motion, whereas for an imaging system, the translation is parallel to the direction of surface motion. Based on this, we discuss a novel method, which is independent of both the optical wavelength and the position of the laser spot on the object, for determining either the angular velocity or the corresponding in-plane displacement of the target object. The out-of-plane angular displacement sensor can be modified to measure the distribution of static torsion angles of targets undergoing twisting motion.15 Because the torsion angle sensor is independent of object shape, we measure the distribution of torsion angles in both uniform and non-uniform deformation zones.
Finally, we present a novel method for measuring out-of-plane angular velocities. Besides measuring angular velocities, the sensor can measure, simultaneously, torsional vibrations of the rotating shaft.
