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Doctor of Philiosophy / This thesis presents my work in the area of optical fibre sensing, and optical fibre design and characterisation along with the interferometric and signal processing techniques that were developed along the way.

Doctor of Philiosophy / This thesis presents my work in the area of optical fibre sensing, and optical fibre design and characterisation along with the interferometric and signal processing techniques that were developed along the way.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2009. / Thesis Advisor(s): Kragh, Frank E. ; Loomis, Herschel H. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: VHF, bridge-to-bridge, interferometry, direction finding. Includes bibliographical references (p. 63-64). Also available in print.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (MPhil) -- AUT University, 2008. / Includes bibliographical references. Also held in print (xviii, 208 leaves : ill. ; 30 cm.) in the Archive at the City Campus (T 681.25 WES)

This thesis is concerned with the design and building of a foot pressure system capable of measuring the pressure distribution underneath the diabetic foot. The system is developed to have a higher resolution and be more cost-effective than existing commercial systems. The biomechanics of the foot and ankle is explained in detail, providing an explanation for the relationship between high pressures and ulcerations. Various techniques of measuring foot pressure are reviewed, providing a thorough understanding of the advantages and disadvantages of each technique. The system developed uses the technique of interferometry, which is discussed in detail, explaining why the Fizeau Interferometer technique was chosen over other interferometer techniques. A number of materials were tested as to their suitability to be used as the pressure plate in the system i.e. compression/force relationship. From the results 'Perspex' was found to be the most suitable material. Two fringe-processing software packages were tested i.e. Fringe Processor 2 and Fringe Pattern Analysis (FRAN), with Fringe Processor 2 being chosen for this research. A graphical user interface for image display was created in order to display and analyse the various pressure images. Three prototypes were implemented. The first used a variation on the Fizeau interferometer, the second used a variation on the Twyman Green interferometer, whilst the third improved on the use of the variation of the Fizeau interferometer. By analysing the advantages and disadvantages of each prototype, the 3 rd prototype was chosen as the most suitable for achieving the aims and objectives of this research. This prototype was subjected to various tests i.e. resolution, measurable area, repeatability, calibration, short term reliability and sensitivity to heat. Various normal and pathological foot measurements were taken and analysed, and the effectiveness of the image display graphical user interface tested. The main contribution of this thesis is the use of interferometry to measure pressure. This in turn provides a foot pressure system, which has extremely high resolution and accuracy. The simple nature of the new pressure system also means that the entire system is very cost effective.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 153-156).

The Bismuth Silicon Oxide (BSO) single crystal can be obtained both in a large size and with good optical quality. It has been demonstrated that the BSO (Bi₁₂SiO₂₀) crystal is a practical holographic recording medium. BSO is a semiconductor and has a large electro-optic coefficient. These two properties of the BSO crystal are responsible for its capability to record. In this study, the linear and circular birefringence of the BSO crystal under an electric field were investigated. The measurement method is by passing a linearly polarized wavefield through the crystal. The transmitted wavefield is written in parametric expressions using Jones calculus, and the wavefield is probed by a simple ellipsometer. The two parameters in the Jones matrix, the linear and circular birefringence, are solved from the experimental data. The electro-optic coefficient is determined from the resulting linear birefringence to be 3.57 x 10⁻¹⁰ cm/V at λ = 632.8 nm. The diffraction efficiency and temporal response of the BSO crystal in the transverse electro-optic configuration were studied. The crystal was then coated with a single layer antireflection coating to investigate the effect of a multi-reflections inside the crystal. The result showed that although the visibility improved only about 20%, the diffraction efficiency and temporal response improved two times. The BSO crystal is used as the recording medium in a two-wavelength holographic interferometer. An optical edge filter is used in the interferometer to adjust the beam ratio, and a prism is used to incorporate tilt in the interferometer and to deviate the two wavelengths to satisfy the Bragg's condition for the volume hologram. The 488 and 514.5 nm lines of an argon-ion laser are used to give an equivalent wavelength of 9.45 μm. The interferograms obtained are of high contrast.

A digital speckle-pattern interferometer was built utilizing a 100 x 100 element Reticon diode array interfaced to an HP-9836C desk-top computer. A single-mode optical fiber mounted in the center of the system's aperture stop creates a spherical-wave reference beam. Secondary interference fringes are calculated inside the computer by subtracting speckle patterns before and after a deformation, and squaring this difference. This technique has been shown superior to that of taking the absolute value of the difference. The traditional vibrational observation technique of low-pass filtering a single speckle pattern and squaring the result is emulated in software. It is compared to four other vibration observation techniques. A new technique records the self-interference terms in a reference frame, and subtracts these from the time-averaged vibration data. It provides very good fringe contrast for moderately unstable objects, as well as interferometers which have not been optimized to minimize self-interference terms. The best vibration fringe contrast is obtained by subtracting two time-averaged speckle patterns of a single object resonance. One exposure has a relative π phase-shift between object and reference beams to cancel self-interference terms. This last technique is not real-time; whereas, the new technique is. Double-exposure speckle interferograms are averaged using a technique which utilizes a stepping motor to change the object illumination angle. Results of averaging deformation measurements and double-exposure vibration techniques show a large increase in fringe contrast with an accompanying reduction in speckle noise. Quantitative measurements of object deformations is demonstrated by applying phase-shifting interferometry techniques. A deformation's phase is found by subtracting modulo 2π phases measured for each object state. Phase discontinuities are removed with the aid of noise reduction algorithms. Limitations are low intensity modulation as the phase is shifted, and speckle decorrelation during object deformation. It is shown that 10 waves of object deformation are measurable to λ/10 across the detector array. The double-exposure phase-measurement technique works well and is applicable to many different metrological measurements. To show the versatility of this technique, an optically smooth surface is contoured using two illumination wavelengths.