The study of intrinsic stress in PVD thin films is rather important because it is related to the films' to substrate adherence, and influences the coated component during service. Stress is strongly induced during the film growth process that is controlled by the deposition parameters. The residual stress of the as-deposited PVD coatings causes bending of the coating/substrate system. If residual stresses are present, but the overall detection is small compared with the substrate thickness, then by symmetry the coated substrate will take up a spherical curvature in the region away from the edges. In this communication we will report on our work on residual stress evaluation of different kinds of thin films, by profilometric optical inspection of the film/substrate system. The inspection system we used, the MICROTOP.06.MFC, is an active optical triangulation sensor developed by the author at the Universidade do Minho. It allows depth resolutions down to 7 nm and lateral resolutions down to 1 )mum.

In view of applications of SiO_xN_ythin films in MOEMS technology, a study of optomechanical characteristics of this material PECVD deposited are investigated. To optimize the quality of SiO_xN_y layers we established the relationship between the chemical properties, optical performances and micromechanical stress of deposited films. To use the SiO_xN_y thin film for the core layer of a channel waveguide, we need to obtain a structure with low optical attenuation, well-controlled refractive index, and low-internal stress. To study the stress characteristics of SiO_xN_y material we used an interferometric technique, and we fabricated for this purpose special membranes with deposition of variable quality SiO_xN_y thin films.

Highly orientated V2O5 thin film was prepared by sol-gel method on SiO₂/Si substrate. When baked at temperature higher than 400°C and pressure lower than 2Pa, the V₂O₅ thin film can be converted to VO₂ thin film. Annealing V₂O₅ thin film under 1-2Pa, 480°C for 20 minutes, the VO₂ polycrystalline thin film with resistance change larger than 3 orders of magnitude and 6.2°C hysteresis width was obtained. Meanwhile the transition progress from V₂O₅ to VO₂ was discussed in detail. It was observed that the valence of V was reduced by the sequence as V₂O₅ to V₃O₇ to V₄O₉ to V₆O₁₃ to VO₂, namely from V_nO_2n+1(n=2,3,4,6) to VO₂. It was confirmed that the key factors to obtain VO₂ thin film with good switching property were the conditions of pre-heating and vacuum baking for V₂O₅ thin film.

Nanosized lead titanate (PT) powder obtained by the Sol-gel method was homogeneously mixed with vinylidene fluoride-trifluoroethylene[P(VDF-TrFE)]. The nanocomposite film was used as the sensing film of PT/P(VDF-TrFE) pyroelectric sensors, whose detective merit was about 20% higher than that of sensors using pure P(VDF-TrFE). Porous silicon with porosity of 69% prepared by electrochemical method was oxidized to porous SiO₂ in wet oxygen. Such porous SiO₂ was chosen as substrate, which can effectively decrease the heat loss due to condition of the substrate. The voltage responsivity was increased and the thermal fluctuation noise of the pyroelectric element was decreased significantly. The experimental results indicated the specific detectivity of PT/P(VDF-TrFE) pyroelectric sensors based on porous SiO₂ substrate was nearly 2 orders of magnitude higher than that of the sensors on bulk SiO₂ substrate formed under the same conditions.

Fringe projection is an often used optical technique for 3-D surface measurements of industrial and biological objects. Classical fringe projection has the disadvantage to determine the surface topgraphy in a quite small unambiguity range only. Gray code techniques are used to solve this problem, but the spatial resolution is reduced due to a small numerical aperture. In a new approach we want to extend the measurement range and we will increase the spatial and the vertical resolution too. This is achieved by a depth-scanning approach together with high numerical apertures for the illumination as well as for the detection. With the aid of an additional z-scanning stage either the object, the sensor, or the image plan are scanned to obtain data over the whole measurement volume. We call this technique depth-scanning fringe projection. It is especially advantageous for the measurement of medium sized objects and can achieve resolutions of less than 0.2micrometers .

A technique is introduced for the industrial surface inspection of workpieces in production lines. This procedure is based on an active technology in optical shape measurement, the so called inverse projected-fringe-technique. After a precise reconstruction of the object shape with respect to the known weak points in the projected fringe technique, a new fringe pattern can be computed and projected using a free-programmable fringe modulator. The objective is to compensate the shape dependent distortions of the fringes. Such an inverse projection can be used for the comparison between a sample and its master piece in quality control. Having a test object that completely fits in shape with the master piece the inverse projection delivers an equidistant and non-distorted fringe pattern under the same observation direction. However, every faulty object area of the sample causes distortions relatively to this known model and can be consequently detected very fast by means of suitable correlation techniques. Especially the simplicity of the master pattern (straight and uniform fringes) offers the possibility of very simple optical filters and the rapid evaluation using an OASLM with an optical correlator (analog) or by applying the spatial heterodyne-technique (digital).

Surface profile measurement using a CD optical pickup head was studied. A simple controller capable of driving the laser diode in the optical pickup head with a power control feature was developed. A simple setup with the optical probe was used for experiments of surface profile measurement. The relationship between the height change and the light intensity received by the photo detector was studied. Hill-shape-like curves were obtained and the relationship was verified experimentally.

Giving a new physical interpretation to the principle of longitudinal coherence control, we propose an improved method for synthesizing a desired spatial coherence function along the longitudinal axis of light propagation. By controlling the irradiance of an extended quasi-monochromatic spatially incoherent source with a spatial light modulator, we generated a special optical field that exhibits high coherence selectively for the particular pair of points at the specified locations along the axis of beam propagation. This function of longitudinal coherence control provides new possibilities in optical tomography and profilometry. Quantitative experimental proof of the principle is presented.

Carrier gratings are generally used to carry the spatial information about surfaces to be inspected and spatial information demodulated using phase shifting methods. Phase shifting methods need more than one image to demodulate the phase information and hence the spatial information of the object. In this paper we propose a method to inspect surfaces by projecting grating patterns on surfaces and Radon transforming the images. Fringe inclination is used as an estimator for locating surface defects.

We successfully developed a new Brillouin-OTDR (BOTDR) that is highly stable in the face of surrounding temperature fluctuations it by employing a microwave heterodyne receiver and a tunable electric oscillator. We were able to realize good frequency and power stability because the BOTDR only pulse-modulates the probe light launched into the sensing fiber. The design is optimized to detect cracks that occur in concrete structures by measuring the strain in a sensing fiber fixed to the concrete structure at a certain level. We demonstrated that the BOTDR could measure the strain in a 10 km long sensing fiber to an accuracy of 10 (mu) (epsilon) (corresponding to 0.5 K in temperature) with an optimum spatial resolution of 20 ns. This accuracy is sufficient given the required strain of 50 (mu) (epsilon) for crack detection. In addition, the BOTDR strain deviation caused by temperature fluctuation was less than several (mu) (epsilon) . The simple design of the BOTDR meant that the measurement time could be reduced to 170 sec.

Dynamic analysis of structures and machines provide valuable information on the performance and reliability of structures. In this paper, we present the development of a Fiber Optic Polarimetric Sensor (FOPS*) for dynamic and impact loading. The sensor monitors the change in the state of polarization of the light beam traversing the fiber under dynamic loading. The dynamic response of three different sensing optical fibers - high birefringence (bow-tie) fiber, low birefringence fiber and an ordinary communication grade single mode fiber are evaluated. The studies were carried out by embedding the optical fibers in a glass fiber reinforced plastic (GFRP) specimen and the performances of the three different systems were compared.

Bragg grating-based sensor devices are popular as they are relatively simple to fabricate and use, but the need for compensation for temperature effects is of particular importance for accurate and reliable measurement of other parameters. Equally, the use of rare-earth-doped fiber has revolutionized many aspects of both communications and sensor systems and recent research has produced fluorescence decay-time and intensity ratio transducer devices which yield reproducible and accurate temperature measurement. This work reports on research carried out on sensor devices using co-located Bragg gratings and fluorescence decay-time sensors, using both separate optical fibers (plain and rare-earth-doped silica respectively) or with the Bragg grating actually written into the fluorescent fiber. The sensor system thus created is simple and effective with a single optical source used to excite both the fluorescence emission (which provides decay time information) and to enable the measure-induced Bragg grating wavelength shift to be determined. With such systems under test, satisfactory strain and temperature resolutions have been achieved. Applications include temperature compensated structural monitoring and monitoring of temperature in structures where the sensors are exposed to strain.

A novel fibre-optic sensing system used for temperature- strain discrimination is presented. This system consists of an extrinsic Fabry-Perot interferometric sensor (EFPI) and a chirped in-fibre Bragg grating (CFBG) in series. The EFPI and the CFBG are wavelength-division multiplexed to provide strain and temperature information, respectively. The wavelength-shift of the CFBG induced by temperature change at the 1.55μm region is interrogated with an intensity- based scheme, allowing fast measurement of temperature. The cavity length change of the EFPI is measured at the 1.3μm region, allowing strain to be measured without cross-talk from the temperature sensor, i.e, the CFBG. Experimental results show that the achieved accuracies for strain and temperature measurement are ±20με and ±2°C, respectively.

Long period fiber gratings (LPFGs) have important applications in fiber sensors because of their high sensitivity to temperature, strain, and refractive index of surrounding medium, et al. In this paper, we demonstrate the bending-induced resonance mode splitting of the LPFG in three different photosensitive fibers (QPS-T)fiber, O/E Land fiber and Fiber Core fiber). For the QPS-T photosensitive fiber, when the grating is bent, the resonant dip shifts to a longer wavelength with a reduction in strength and a new dip emerges at a shorter wavelength. The wavelength separation between the new dip and the original one is linear with the deflection of the grating. The similar results are also observed in two other LPFGs. But when the grating is bent, the original dip of grating shifts to a shorter wavelength and the new dip shift to longer wavelength. The different bending properties of the LPFGs are observed in the different photosensitive fiber, which is attributed to the different fiber parameters. For the LPFG written in the QPS fiber, the bending and temperature properties of the dip corresponding to the LP₀₉ mode is studied experimentally. Based on the property that the new dip induced by the bending of fiber has the same temperature sensitivity with the original one, a temperature-insensitive curvature sensor is proposed by measuring the wavelength separation of the two dips.

Simultaneous strain and temperature measurement for advanced 3D braided composite materials using fiber-optic sensor technology is demonstrated, for the first time. These advanced 3D braided composites can virtually eliminate the most serious problem of delamination for conventional composites. A tandem in-fiber Bragg grating (FBG)/extrinsic Fabry-Perot interferometric sensor (EFPI) system with improved accuracy has been used to facilitate simultaneous temperature and strain measurement in this work. The non- symmetric distortion of the optical spectrum of the FBG, due to combination of the FBG and the EFPI, is observed for the first time. Experimental and theoretical studies indicate that this type of distortion can affect the measurement accuracy seriously and it is mainly caused by the modulation of the periodic output of the EFPI. A simple method has been demonstrated to improve the accuracy for detection of the wavelength-shift of the FBG induced by temperature change. A strain accuracy of ~+/- 20(mu) (epsilon) and a temperature accuracy of ~+/- 1 degree(s)C have been achieved, which can meet the requirements for practical applications of 3D braided composites.

We report a fiber Bragg grating sensor for the measurement of static and dynamic measurands (e.g., strain and temperature). Initial experiments demonstrated detection resolutions of ~2.6me and ~7ne/(Hz)1/2 for static and dynamic strain measurements respectively.

An approach to compensate atmospheric disturbances in free space laser communication systems by means of dynamic holograms is considered. The possible architectures are discussed. The requirements to dynamic holographic media re specified and candidate materials are listed. Results of a modeling experiment on dynamic phase compensation in BSO crystal are presented.

Although developments of underwater robotics vehicles (URV) have been rapid in recent years, the underwater vision sensing is still regarded as a major tough undertaking, particularly in turbid water condition. Currently, a Underwater Lidar Imaging (UWLI) sensing system has been finished and demonstrated nano-second level gated images in highly turbid water. It permits to keep underwater vision sensor with optical resolution but reduce the optical scattering noise in water dramatically. Based on our newly- designed series targets at intervals of 22.5cm, we are first to study UWLI in such a 3m short tank successfully. The system could be synchronized precisely to range-gate the targets which we want to have its image, and to gate out the targets which we don't want its image. The attenuation coefficients of highly turbid waters are 1.0/m and 2.3/m. Compared with non-gated photos, the most distinct difference between the gated imaged and non-gate images in turbid water is that the nearer the target is located, the clearer its image is on the non-gated photos, but for the gated case the situation will be inverted completely when the time-delay is set suitably, i.e. the image of the farther target could be much clearer than the image of the nearer target in very turbid water.

Tele-shearographic system based on bulk optics shearing and optical fiber based illumination have been used for the Non-Destructive Testing (NDT)of aircraft/composite laminates. This paper describes the application of this system and a detailed experimental analysis to assess defects in Carbon Fiber Reinforced Plastic (CFRP) composite laminates by analyzing the fringe patterns. CFRP laminates and honeycomb panels have been studied using the this system in various optical configurations. This technique provides the full-field, non-contact method for Non-Destructive Evaluation (NDE) of composite specimens. A Comparative study between digital shearography and other NDTechniques are also discussed in this paper.

In this paper we describe a new sensor for the direct holographic comparison of the shape of two objects where it is not necessary that both samples are located at the same place. In contrast to the wellknown incoherent techniques based on inverse fringe projection this new approach prefers a coherent mask that is overlayed to the sample object having different microstructure. The coherent mask is created by digital holography to enable the instant access to the complete optical information of the master object at any wanted place. The transmission of the digital master holograms to the relevant places is done with a broadband digital telecommunication network such as the Internet. The availability of the complete optical information of the master object in the form of its digital hologram offers two ways with respect to the comparison of its shape and/or deformation with those of a sample object having different microstructure: digital comparison of the respective phase distributions of the relevant digital holograms and analogue comparison of both holograms/interferograms by digital comparative holography.

Intra-cavity spectroscopy is a highly sensitivity technique for absorption measurements and has been a subject of interest for many years. In this paper, we report the results of our experimental investigations on intra-cavity gas (acetylene) absorption measurements with a wavelength tunable fiber laser. The intra-cavity spectroscopy systems are all fiber systems and have the potential of being used for compact field spectroscopic measurements.

With the increasing demand for micro-products and bioengineering research, resolutions of profiles with micrometer or even nanometer scale are becoming commonplace. In addition development of large integrated manufacturing systems and the real time life science growth and adaptation need high-speed display and real-time inspection. Single point measurement is time consuming method with large area profile and micrometer resolution. Thus there is a need for a fast 3-D measurement system with high resolution. This paper presents a short overview among optical 3-D shape measurement techniques, and concentrates on the confocal method. Based on the properties analysis, a novel multi-channel 3-D topography measurement system was proposed. The feasibility and the construction of system were described A unique new structure of fiber coupled confocal system is put forth to solve present problems confronted in confocal system. This system can meet the current demand of high resolution and fast 3-D measurement.

Liquid crystal displays, originally designed and fabricated for projection systems, are often used as spatial light modulators in optical correlators or in fringe projection systems. Operating in a linearized phase mode, they can achieve a performance to be applicable as diffractive elements. An adapted driver electronics and adapting measurements of the phase modulation behavior can lead to a dynamic phase modulating system with an almost linear modulation and a maximum phase shift of 2(pi) . The electronic system can directly address the graphics card signal or can picture various video standards. So, computer generated holograms can be addressed at video frame rates. The limiting parameters of the performance are mostly due to physical boundary conditions, such as pixel number and size, response time, transmission etc.. We can assume that the fast growing micro-structuring technology will serve us soon with displays of higher resolutions and efficiency. Beam shaping elements, two-dimensional holograms and the reconstruction of digital holograms will be shown. The latter opens new possibilities for non-destructive testing devices especially in the field of holographic interferometry. We will show results of different systems and derive boundary conditions for applications in holographic reconstruction of coherent masks.

In this paper, we present a design of a phase-only diffractive optical element (DOE), which is capable of producing two distinct diffractive patterns for two wavelengths with high and equal diffraction efficiencies. The DOE is constructed by two one-sided surface profiles that are stacked together and in contact with a thin focusing lens. One is designed for a wavelength of the incident light to generate a pattern on the back focal plane, and the other is for the second wavelength to generate a different diffractive pattern without affecting the first pattern. The second profile simply provides a multiple of 2(pi) phase delay for the first wavelength and thus has no effect on the first pattern. In the proposed algorithm, the iterative Fourier transform algorithm with the stepwise quantization method is modified to calculate the two phase profiles simultaneously in the iterations. High and equal diffraction efficiency (74.5%) for the two wavelengths was achieved with 2 phase profiles of 4 uniform phase levels. In addition, a method of multiple bounding controls was proposed to increase the SNR in the regions of interest so as to improve the chromatic performance of the double wavelength design. Different SNR's (5.7 dB and 1.7 dB) were achieved at signal and noise regions.

We present a novel optimal phase quantization method for phase-only diffractive optical elements (DOEs) by taking into account both amplitude and phase information that are able to generate an arbitrary target pattern. In our approach, the MSE function was modified in which both the amplitude and the phase of the perfect wavefront were combined into the probability density function. The amplitude and the phase information could be obtained from a phase transmittance of a transparent lens incident by a Gaussian beam (providing the amplitude information), for example, or be directly constructed from the inverse Fourier transform of an arbitrary target pattern. By using the modified MSE function, the influence of the phase elements corresponding to larger amplitude values was emphasized and the optimal phase levels were calculated appropriately. Significant improvement was achieved for the construction of two-, four-, and eight-level Fresnel zone plates with a focal length of 8 m and an aperture of 6.2 mm, which was incident by a Gaussian beam with a 1/e-width of 1.4 mm were calculated. By use of the proposed algorithm, efficiency improved by 26.4% and SNR by 18.2% over the uniform quantization method for binary DOE's.

The objective of this project is to apply photonics technology to bio-safety management of genetically modified (GM) plants. The conventional method for screening GM plants is through selection using antibiotic resistance markers. There is public concern with such approaches and these are associated with food safety issues, escape of antibiotic resistance genes to pathogenic microorganisms and interference with antibiotic therapy. Thus, the strategy taken in this project is to replace antibiotic resistance markers with fluorescent protein markers that allow for rapid and non-invasive optical screening of genetically modified plants. In this paper, fibre optic spectroscopy was developed to detect and quantify recombinant green (EGFP) and red (DsRED) fluorescent proteins in vitro and in planta. In vitro detection was first carried out to optimize the sensitivity of the optical system. The bacterial expression vectors carrying the coding regions of EGFP and DsRED were introduced into Escherichia coli host cells and fluorescent proteins were produced following induction with IPTG. Soluble EGFP and DsRED proteins were isolated from lysed bacterial cells and serially diluted for quantitative analysis by fibre optic spectroscopy using different light sources, namely, blue LED (475 nm), tungsten halogen (350 - 1000 nm) and double frequency Nd:YAG green laser (532 nm). Fluorescence near the expected emission wavelengths could be detected up to 320X dilution for EGFP and DsRED with blue LED and 532 nm green laser, respectively, as the excitation source. Tungsten halogen was found to be unsuitable for excitation of both EGFP and DsRED. EGFP was successfully purified by size separation under non-denaturing electrophoretic conditions and quantified. The minimum concentration of EGFP detectable with blue LED excitation was 5 mg/ml. To determine the capability of spectroscopy detection in planta, transgenic potato hairy roots and whole modified plant lines expressing the fluorescent markers were regenerated. T

This paper reports on work done with a range of silica fibres, doped with several important rare earth ions such as Er, Nd, Yb and Tm, to create a range of novel optical sensors. The approach reported herein is based on monitoring and analysis of the fluorescence decay from such fibres in the time domain as well as in the frequency domain. With these fibres, temperature sensors operating in the range from as low as -200 degree(s)C to beyond 1000 degree(s)C have been constructed. A temperature resolution of the order of a few degrees Celsius has been typically reported from these types of sensors. Fibre of this type has been used in a simple yet effective structural integrity monitoring system (being incorporated successfully into concrete samples) and an optical fire alarm system with potential applications for engine monitoring has been developed. A further recent discovery is a small level of strain sensitivity in such fibres - this has been explored over the region from 0 to 2000(mu) e, showing a level of resolution better than a few tens of microstrain, and sensors based on this effect are discussed and reported on in this work.

The method of vibration signal processing for interferometric optical fiber sensor is presented in this paper. For stable vibration, the method of frequency spectra analysis is used. For random vibration, using the system of fiber optic sensor in special coherence combined digital image processing setup and recording to moved number and direction of interferometric fringe and physical formula, collecting and processing image signal of vibration state is presented and professional software is studied and stress-time curve under random vibration state is measured after stress-time curve and vibration frequency for stable vibration were measured where they correspond with theory solution. This research provides a kind of new method for vibration monitoring of structure engineering.

Recent advances in micro electronics and electronic packaging have led to a strong need in material characterization on micro and nano scale. The authors present an approach to deformation measurement based on localized correlation analysis on load state images. Displacement and strain fields are extracted from images, captured by high resolution equipment, e.g. by optical far distance, scanning electron and scanning force microscopes. As a result object response to mechanical or thermal load can be recorded from microscopic or nanoscopic material areas. Within the paper a brief overview is given about measurement basics, achievable measurement resolution and equipment. The method is being applied to thermo-mechanical reliability studies on electronic packaging components. As an example stress suppression mechanisms on advanced chip scale packages (CSP) have been investigated. Spatially resolved deformation measurement by correlation techniques could have been extended successfully to AFM imaging. A corresponding application is demonstrated for experiments on microcrack evaluation. In order to measure material properties a modified correlation algorithm is applied assuming homogeneous material response. Determining average strains over micrographs material properties as coefficients of thermal expansion (CTE) and Poisson ratios can be determined on micro objects.

In this paper, a quantitative method to measure simultaneously micro-stress and strain is proposed. A compact optical transmitting microscope is reconstructed by developing a loading and recording system, and white light source can be replaced with a laser source. The choice of laser source or white light source depends on the thickness of specimen. For strain measurement, grating diffraction method is presented. With the help of a Bertrand lens, the Fourier spectrum of the grating is formed on the CCD sensor plane or with high image quality. Software for precise, fast and automatic determination of the diffraction spot centroids is developed. Local strains are thus measured with high resolution. Stress measurement is carried out to the zero order of grating diffraction spots following the conventional method for retardation measurement with tilting compensator. The combination of the grating diffraction method and the photoelasticity method in the same test provides simultaneous measurement of strain and stress.

The full field moire interferometry and the micro moire interferometry were applied to investigate the thermo-mechanical deformation induced by thermal loading in electronics packages. The packages investigated were flip chip and flip chip ball grid array (BGA) packages. The solder alloys used in the packages were eutectic solder, tin silver solder and tin silver copper solder. Thermo-mechanical deformations and shear strains generated from CTE mismatch were determined experimentally using a holographic grating. Micro-deformations within the solder joints of the flip chip packages were captured and analyzed. The results showed that micro moire interferometry was effective in micro-deformation measurement. The thermally induced shear strains in the underfilled flip chip packages increased almost linearly with distance from the neutral point. The outermost solder joints suffered the highest shear strains. For flip chip BGA packages on FR-4 boards, the solder joints under the die corners had the highest shear strains. High shear strains were also observed at the underfill fillet. The performances of the two lead-free solder alloys, tin silver solder and tin silver copper solder, were compared with that of the conventional eutectic solder. It was found that tin silver solder joints had the highest shear strains whereas the shear strains for tin silver copper solder were comparable with or lower than those of eutectic solder.

In this paper, the electron beam moire method and AFM scanning moire method are proposed to measure in-plane deformation in micro-scale. The measurement principle and techniques of these two methods are discussed in detail. Additionally, the phase shifting AFM moire method is advanced. The methods are used to measure the thermal deformation in the BGA and QFP electronic packages. The successful results verify the electron beam moire and AFM moire methods are effective tools for measuring micro-scale deformation.

We have fabricated and tested an external cavity laser with a micromachined flat polysilicon micro-mirror. The device works using a very short external cavity laser configuration (approximately equals 10micrometers ) allowing to remove all optical element in the cavity while providing enough feedback to modulate the intensity of the laser. We have shown that we could obtain feedback coefficient larger than 0.5, providing an increased sensitivity for sensor application. The device shows interesting characteristics for developing a compact and simple displacement/acceleration sensor with large dynamical range and a resolution estimated below 0.01 nm.

We describe direct measurement of phase of ballistic photons transmitted through objects hidden in a turbid medium using a polarization interferometer employing a rotating analyzer. The unwrapped phase difference measurements from interferometry was possible for medium levels of turbidity and accurate phase measurement from the sinusoidal intensity was not detectable when l/l* is increased beyond 4.3. The measured phase on reconstruction using standard tomographic algorithms resulted in the recovery of the refractive index profile of the object hidden in the turbid medium.

The application of phase-shifting photoelasticity to real- time dynamic event involves simultaneous recording of the four phase-shifted images. This purpose is realized in this paper by using a special beam-splitting lens called Multispec Imager. The isoclinic and isochromatic parameters for a given time in a dynamic event are determined by using multi-load to phase-shifting technique. A modified median filter algorithm for wrapped phase data is also presented.

In interferometric fringe pattern analysis, specular and speckle fringe patterns are the two main divisions. While specular fringes are characterized by quality fringes with high spatial resolution, speckle (that obtains due to the diffuse scattering of the coherent radiation from an optically rough surface) fringe patterns, which contain high frequency carrier (as noise), are characterized by noisy fringes. This paper concentrates on this aspect and the matlab based filtering methods to improve 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 post-processing of the speckle interferometric fringes. The algorithm and functions of the developed software Macurv will be explained.

It is interesting and useful to note that, even without carrier, the fringe pattern can still be processed for phase retrieving by Fourier transform method. A key problem is its phase retrieving accuracy, which is the topic of this paper. Our analysis shows that in some cases this method may introduce large phase errors and should be used with care.

In our earlier work, a group of error-compensating phase shifting algorithms with known phase step of (pi) /2 has been derived, and the optimal phase steps for Carre algorithm and Stoilov-Dragostinov algorithm were determined and a good and recommended choice is also (pi) /2. This paper gives a further evidence of error compensating merits of these algorithms. Theoretical analysis, as well as computer simulation is given for evaluating the phase errors due to the most common error sources, such as linear and quadric phase shifter errors, quadric detector error and additive random error.

In this paper we discuss an application of CMOS photo-sensor array chip using pulse frequency modulation (PFM) to sub-retinal implantation to recover human vision. PFM with integration mode as photo-sensing circuit is used to realize enough dynamic range and compatibility with signals in real retina. To effectively stimulate the retinal cells, we have designed a PFM circuit with limited bandwidth of output pulses and two kinds of pulse shaping circuits with digital waveform memory and pixel-level output amplitude tuner. We have fabricated a PFM photo-sensing test circuits with a standard 0.35 micrometers CMOS technology to measure its basic characteristics, and have demonstrated a large dynamic range of around 40 dB.

An optical fibre (3 sensor) multipoint U-Bend evanescent wave absorption sensor system is reported which is capable of detecting contaminants in water and depositions by coating on its surface. The sensor is based on a continuous 1Km 62.5micrometers core diameter Polymer Clad Silicon (P.C.S.) fibre which has had its cladding removed in the sensing areas. The sensing fibre is addressed using an Optical Time Domain Reflectometer (OTDR), and is thus capable of resolving distance along its length allowing measurement at multiple points on a single fibre loop. Signals arising from optical fibre sensors can often be complex in nature and this is particularly so in the case of multipoint sensors. Due to cross-coupling effects of interfering parameters, it is difficult to interpret data from such systems using conventional detection techniques. Artificial Neural Network pattern recognition techniques are used for the signal analysis of the sensor, which allow classification of the samples under test, thus allowing the true measurand to be recognized and separated from any cross-coupling effects that may be present. The system described is capable of recognizing cross-sensitivity from interfering parameters such as lime scale coating in hard water and the presence of other species e.g. alcohol in the water. Results are included that have been obtained from the sensors OTDR data. Also presented, are the resulting test outputs that have been obtained from a trained feed-forward neural network designed to interpret the sensor data. The system was 100% successful in classification of all test samples analyzed.

Diffractive optical element (DOE) can be used to realize beam smoothing. In order to realize true beam smoothing, a new design method with a more restrict way in the optimization has been proposed. In this paper, based on this new design method, polarization design is adopted to improve the performance of the DOE for true beam smoothing. The top non-uniformity can be held to be less than 2.7%, no matter which group of sampling points on the focal plane is chosen to be calculated.

A rigorous numerical model has been developed to study Ti:LiNbO₃ Mach-Zehnder interferometric (MZI) modulators. In this present study a comparison was made between an unetched waveguide and an etched Ti:LiNbO₃ ridge waveguide Mach-Zehnder interferometric (MZI) modulator in order to show the benefits of using edged ridge waveguides for the MZE modulator. In this study, it was shown that the modulator could be improved further by manipulation of the appropriate fabrication parameters.

A spatially multiplexed high bandwidth WDM based fibre Bragg grating sensor system has been developed for structural condition monitoring and health maintenance of large civil engineering structures under both static and dynamic loading conditions. The system has been field deployed for real-time strain monitoring on a new 346m long steel road bridge in Norway. The bridge was instrumented with both fibre Bragg grating sensors and conventional resistive strain gauges at various points optimally identified. In this paper laboratory results from small-scale structures as well as field results on the real bridge structure are reported.

We report an amplitude division multiplexed interferometric sensor array for locating acoustic emission. The interferometer is composed of 3 arms, the two sensing arms have different interference amplitude with the reference arm, so we can judge whether a sensor receives sound or not from the composite interference amplitude. For single sound source, the sound-receiving delay of two sensors can be obtained from the time when the interference amplitude changes, and the sound source location relative to the sensors can also be achieved in a 1-D system. Preliminary experiments were carried out and demonstrated a one-dimensional (1-D) location accuracy of better than 1cm. The system can be extended for 2-D and 3-D location of acoustic emissions by adding one or two more sensing arms, respectively, in the interferometer.

In Fourier transform method for carrier fringe pattern processing, the variety of windows used is compared for their phase retrieving accuracy by computer simulations. The results show that, (1) Two dimensional Fourier transform method is better than the one dimensional transform; (2) The phase errors at image edges are large and should be discarded; (3) No new windows are needed since it is unlikely to improve the phase retrieving accuracy.

Non-destructive profiling of the front and rear surfaces of a transparent media by optical interferometry is described. Interferometric measurement of a transparent parallel media leads to problems of multiple-beam interference noise between the two surfaces. A wavelength scanning interferometer with new sampling functions can determine both surface shapes simultaneously suppressing internal reflection noises less than order of R²(lambda) where R is the reflection index of the media and (lambda) is the source wavelength.