In many industrial applications, the material surface is, most of the time, the preponderant factor in the life time of a piece. In such cases, it is relevant to be able to improve the superficial properties of the material. To do so, on solution: the laser cladding process, consists in deposing a hardfacing alloy where the constraints are more likely to occur. The process involves the delivery of fine grained alloy powder blown into the melt pool during the laser irradiation. In a coaxial delivery system, the powder spray distribution as well as the grain speed have a tremendous impact on the process efficienty. We herein present different experimental methods enabling to assess the particle speed as well as their distribution within the spray. Our configurations employ a laser sheet illumination of the power spray, a CCD camera and a PC to process the obtained images. In order to study the power distribution versus the nozzle distance, the laser sheet was moved away from the nozzle with low incremental steps such as to establish a profile of the spray. For speed measurements, various configurations were used. Images either manually processed or automatically using algorithms such as Hough, or Fourier Transform.

Many industrial and fossil fuel energy processes involve two phase flows for mass transit. In order to improve and better understand these two phase flows, knowledge of both the droplet/particle size and spatial distribution are required. The useful diagnostic tools should be able to make in-situ measurements without disturbing the flow field so that undisturbed flow measurements can be obtained. This suggests the need for a novel non-intrusive optical technique that can provide instantaneous measurements of particle size and velocity at multiple spatial points in planar (2-D) fields. Digital Particle Image Velocimetry (DPIV) is being studied as a candidate technique for making these measurements. A Monte-Carlo simulation has been developed that simulates the PIV optical recording system and the electric field scattered from particles in the flow. The simulation incorporates diffraction and the variation in light sheet intensity across the depth of field of the optical system. The simulation also computes the Mie scattered electric fields and images these onto the CCD detector. For small size particles, diffraction effects of the optical system dominate the recorded particle image light intensity distribution on the CCD array, and precludes our ability to determine their size. However, for larger sized particles other effects become more dominant, such as the glare spots in optically clear particles. The simulation allows us to examine the Mie scattered electric field of the particles recorded on the CCD and use the higher order structure in the recorded images to determine particle size. A technique for sizing is proposed which uses the separation between two glare spots visible on the particle image to estimate the particle diameter. The results show that the input particle size distribution to the simulation can be reasonably reproduced using the proposed sizing technique. Analysis of experimental PIV images also demonstrated that this technique is capable of providing moderate accuracy particle size estimates.

Optical tomography involves the use of non-invasive optical sensors to obtain information in order to produce images of the dynamic internal characteristics of process systems. This paper presents an investigation using optical tomography suitable for determining concentration and velocity profiles in two component flows in a fluid conveying pipe. The system is capable of detecting and measuring the amount of undissolved gas in waster, or gas in oil, where the mixture is flowing in a pipe. The system employs four projections consisting of a combination of two orthogonal and two rectilinear projections. The light transmitters consists of four halogen bulbs. Each orthogonal receiver projection employs 8 sensors and each rectilinear receiver projection uses 11 sensors making a total of 38 receiver sensors. The voltage profile from the sensors gives spatial information of the flow regime. Signal processing provides time-averaged signals which will generate peripheral concentration profiles. To observe the velocity profile via cross- correlation, a second identical measurement system has been constructed. One array of sensors is positioned upstream and the other downstream in the process measurement. Cross-correlograms provide mean velocities of velocity profiles over the measurement section.

Laser imaging technologies are now being used in practical combustors, from fuel vapour concentration measurements to liquid drop sizing. Simple 2D imagine has demonstrated its capabilities but has limitations in proving all the required data. Multi-dimension and multi-scalar imaging are demonstrating their power in providing additional information. This paper presents the progression of imaging from 2D to 4D and the advantages gained from the labour intensive multi-imaging processes. Temperature and fuel distribution are of critical interest in most practical combustors. Techniques ranging from simple Planar Laser Induced Fluorescence (PLIF) to more complex multi-scalar techniques such as Laser Sheet Drop-sizing (LSD) and mixture fraction imaging are presented with their potential diagnostic power. Although 2D imaging can provide a great deal of data for axi-symmetric flows, most combustors require characterisation with multiple 2D layers to assemble a fu ll 3D picture of the processes involved. Data is presented for a turbine combustor, showing the development of fuel mixing in the premix duct. The advantages of the complex 4D imaging are shown by the success of fuel imaging in an internal combustion engine where crank-angle resolved images enable the fuel distribution in the combustion cycle and cycle to cycle fluctuations to be quantified.

Planar laser-induced fluorescence (PLIF), planar Mie scattering (Pmie), and linear)1-D) spontaneous Raman scattering are applied to flame tube and sector combustors that burn Jet-A fuel at a range of inlet temperatures and pressures that simulate conditions expected in future high-performance civilian gas turbine engines. Chemiluminescence arising from C₂ in the flame was also imaged. Flame spectral emissions measurements were obtained using a scanning spectrometer. Several different advanced concept fuel injectors were examined. First-ever PLIF and chemiluminescence data are presented from the 60-atm gas turbine combustor facility.

In order to meet the demands of increasingly detailed investigations of processes and phenomena in the flow of compressible fluids, flow visualization techniques have to be brought to a level that allows one to extract both qualitative and quantitative information about a flow field. This contribution presents a brief description of two density- sensitive techniques, holographic interferometry and colour schlieren, which have been shown to be very suitable for this task. Some applications demonstrate the diagnostic potential of these techniques.

We have recently proposed a variant of holographic particle image velocimetry (HPIV) to measure three-component measurements of fluid velocity throughout an extended flow volume. In essence the technique uses double exposure holography to record the positions of seeding particles at two, close spaced constants in time. Analysis of the resulting record is achieved by computing the auto (or cross) correlation of the complex amplitude distributions transmitted by a sampling aperture placed within a real, reconstruction of the holographic image. IN the case of sparsely seeded flows, it is straightforward to show that the field transmitted by the aperture is dominated by the particle images reconstructed close to the aperture itself and the measurement is therefore attributed to the instantaneous flow velocity at the centre of the aperture. As the seeding concentration is increased, however, a significant contribution of the transmitted field is due to light scattered from more distant particles. If significant velocity gradients exist, the contribution due to distant particles is largely un- correlated and the local particle displacement can be extracted even if the field is dominated by this component. If a significant proportion of the scattered light that passes from the aperture is collected from areas in the flow with similar velocity (for example from stagnant regions or light scattered from the flow vessel) then spurious peaks can occur in the correlation signal. This paper examines the limitations on the flow volume that can be mapped at a given seeding concentration and hence the fundamental limits on the number of velocity measurements that can be retrieved from a single recording.

This illumination system is one component of a holographic camera, which is part of a multi-disciplinary, multi-national project (funded by the European Commission MAST III initiative) to use holography for the in situ recording and subsequent analysis of holograms of marine organisms and particles. Laboratory experiments have shown that the best results for off-axis recording are obtained using side illumination. Our design goal has been to provide even side illumination throughout the recording volume. This illumination system, the lightrod, is based on a cylinder made from a transparent material containing a series of partial reflectors inclined and spaced along its length. An unexpanded laser beam is fed into the cylinder along its axis. Each reflector diverts a fraction of the beam into the recording volume. Two versions of the lightrod have been designed and built. In one version, the cylinder uses solid Perspex spacers with a small air gap in between; in the other, the spacers are hollow with thin glass windows in between. Both lightrod designs are discussed together with an analysis of the illumination profile, and their practical implementation is outlined. Both lightrod prototypes have been tested in an observation tank. Results from these tests are presented.

The HoloCam system is a major component of a multi-national multi- discipline project known as HoloMar (funded by the European Commission under the MAST III initiative). The project is concerned with the development of pulsed laser holography to analyse and monitor the populations of living organisms and inanimate particles within the world's oceans. We describe here the development, construction and evaluation of a prototype underwater camera, the purpose of which is to record marine organisms and particles, in-situ. Recording using holography provides several advantages over conventional sampling methods in that it allows non-intrusive, non-destructive, high- resolution imaging of large volumes (up to 10⁵ cm³) in three dimensions. The camera incorporates both in-line and off-axis holographic techniques, which allows particles from a few micrometres to tens of centimetres to be captured. In tandem with development of the HoloCam, a dedicated holographic replay system and an automated data extraction and image processing facility are being developed. These will allow, optimisation of the images recorded by the camera, identification of species and particle concentration plotting.

Pulsed laser holography in an extremely powerful technique for the study of particle fields as it allows instantaneous, non-invasive high- resolution recording of substantial volumes. By relaying the real image one can obtain the size, shape, position and - if multiple exposures are made - velocity of every object in the recorded field. Manual analysis of large volumes containing thousands of particles is, however, an enormous and time-consuming task, with operator fatigue an unpredictable source of errors. Clearly the value of holographic measurements also depends crucially on the quality of the reconstructed image: not only will poor resolution degrade the size and shape measurements, but aberrations such as coma and astigmatism can change the perceived centroid of a particle, affecting position and velocity measurements. For large-scale applications of particle field holography, specifically the in situ recording of marine plankton with Holocam, we have developed an automated data extraction system that can be readily switched between the in-line and off-axis geometries and provides optimised reconstruction from holograms recorded underwater. As a videocamera is automatically stepped through the 200 by 200 by 1000mm sample volume, image processing and object tracking routines locate and extract particle images for further classification by a separate software module.

In this study, the method of digital phase shift holographic interferometry is applied to accurately measure the density distribution behind a weak shock wave. The goal of this investigation is to visualize and quantitatively evaluate flow fields behind weak disturbances, which are only marginally stronger than sound waves. In the present experiment, the shock Mach number was approximately M_s approximately equals 1.01. The wave was generated by the explosion of a small silver-azide (micro- charge) pellet, which was ignited by an Nd:YAG laser. Using phase shift interferometry, the phase distribution of the region far behind the incident shock could be detected.

The application of optical metrology using Electronics Speckle Pattern Shearing Interferometry (ESPSI) in industry, is becoming more prevalent as a method of quality assurance and non-destructive testing (NDT). ESPSI provides non-contact full-field inspection of the test object generating displacement derivative data. The trend of using ESPSI in quality assurance in NDT involves the desire for quantitative measurement. ESPSI may be used for out-of-plane displacement derivative (slope) measurements ((delta) w/(delta) x) or potentially in-plane slope measurements (such as (delta) u/(delta) x), depending on optical configurations and object boundary conditions. Current concern is focussed on accuracy of commercial ESPSI systems and questioning the extent of error compensation in the associated fringe software systems. This paper presents studies which have been analyzing in-plane derivative measurement accuracy, as a function of object illumination wave-front divergence. Theoretical error analysis supported by experimental analysis has been performed using restrained aluminum alloy cantilever beam. The relative error is measured by comparing displacement derivative data of measurements using divergent illumination with respect to collimated illumination. The measurement error has been found to be dependent on the direction of illumination and the shearing amount at a fixed distance, with certain combinations producing values exceeding 30%.

Hot stamping foils are used in the printing industry to achieve metallic effects on packaging, pseudo-holographic images for security applications, and other products. The performance of the foil in the stamping process is in part determined by the thickness of the release coating on the carrier foil. This coating is too thin (approximately 10nm) for successful application of conventional measurement methods. We describe a fluorescence-based optical technique to measure the thickness of this release coating on-line. A fluorescent rhodamine dye added to the release coating allows excitation and detection in the visible part of the spectrum. Multimode optical fibre is used for excitation beam delivery and signal collection from a probe head situated on the coating machine. We outline the system calibration and show some representative results form industrial trials.

This paper provides an overview of some of the main competing optical technologies on which future commercial wholefield shape measurement systems are likely to be based. The methods range from those based on pointwise techniques, such as laser triangulation and laser radar, to wholefield techniques such as projected fringes, Gray code methods and white light interferometry. Data analysis procedures including phase shifting and phase unwrapping are also described. The main error sources limiting the performance of the techniques are presented, and their current and prospective performances are assessed in view of recent developments in components such as computers, solid state cameras, and semiconductor lasers.

We describe an extension of the active homodyne technique to produce stabilised, (pi) /2 radian phase steps in a full-field interferometer. We have implemented the technique in a single mode fibre optic fringe- projector for shape measurement. The interference intensity (and hence phase) is maintained constant by feedback control to a phase modulator in one of the fibre arms. The feedback system has been modified to produce (pi) /2 radian phase steps in the projected fringes. The phase stability and accuracy of each step was measured to be 17 milliradians in a 50 Hz bandwidth. The technique can be used to produce stabilised phase-stepped images in any fibre or bulk optic interferometer where active homodyne feedback control can be implemented.

Electronic Speckle Patterin Interferometry (E.S.P.I.) is a holographic interferometry technique technique that can be used to measure out-of- plane deformations and vibration amplitudes up to a few microns with an accuracy of a few nanometres, in near real time. Two-wavelength holographic contouing is an adaptation of this technique that utilises two lasers in an E.S.P.I. system, generating fringes with spacing determined by the frequency difference between the two lasers. Careful choice of laser wavelengths enables us to measure the shape of an object on a scale and accuracy that is more useful in engineering applications. In addition, by measuring the shape of an object before and after the application of a static load, deformation can be measured on this same enginering scale. The engineering drive for this technology is to gain high spatial resolution modal information on light structures (e.g. body panels) with a non-contacting measurement device. The shape and vibration data can then be mapped to each other on a pixel to pixel basis, giving over a quarter of a million data points containing position, vibration amplitude and vibration phase information. This data can then be used to create hybrid Finite Element/Experimental models or be used to predict the noise radiation levels from a vibrating object. In the system described here the 2 laser wavelengths are applied simultaneously giving the capability to obtain the object shape in an engineering environment, i.e. away from a stable optical table. The model data is obtained in a similar manner and therefore the complete system is operable in engineering laboratories.

Heterodyne interferometry is a powerful method to measure the shape of surfaces. However, to the present day there are only a few papers devoted to the analysis of the influence of an interferometric optical system on measurement results. The analysis can be related to its geometrical configuration and optical system aberrations. The problem is particularly important for full field heterodyne interferometry, where the aberrations are different for different field points. The measurement method idea of the registration of travelling fringes with a fast CCD camera and theoretical considerations supported by computer calculations are presented. The harmonic approach to optical imaging is the base to analyze the influence of geometrical and aberrational parameters on the measurement results for a chosen object. The complete optical system is proposed and the measurement results obtained in the laboratory are discussed.

In the paper the sequential steps of reverse engineering based on the data gathered by full-field optical system are discussed. Each step is concerned from the point of view of its influence on the final quality of the shape of manufactured object. At first the modern shape measurement system based on the combination of fringe projection, Grey code and experimental calibration is presented. The system enables the determination of absolute coordinates of the object measured from many directions. The dependence of the quality of the cloud of points on the type of object and the measurement procedure is discussed. Then the methods of transferring the experimental data into CAD/CAM/CAE system are presented. The quality of the virtual object in the form of closed triangular mesh is analyzed. Basing on this virtual object the copy of initial body is produced and measured. The accuracy of the object manufactured is determined and the main sources of errors are discussed. The modifications of the system and algorithms that minimize the errors are proposed. The reverse engineering sequence is presented is illustrated by several examples.

Breaking barrier of the mass production of novel materials (composite, smart, enhanced by surface layers) and introducing new technologies (laser processing, joint between nonconventional materials) pose new requirements for the industrial systems of full-field strain analysis. This quality of experimental data has to be sufficient to introduce them into numerical analysis (FEM) to perform complicated modelling of fracture mechanics, fatigue process or residual stress distribution. The experimental method, which fulfills the quality requirements, is grating interferometry. In the paper the novel type of laser full-field extensometer based on four-beam grating (moire) interferometry is presented. It is designed for medium size field of view (6 x 4.5 mm²). The extensometer is integrated and works directly on a standard loading machine with the possibility to control the load on the base of local on-line strain measurements. It enables the measurements during static, monotonic and cyclic loads and full-field analysis of arbitrary sequence of images. The extensometers give high contrast and good quality interferograms, are insensitive to vibrations and work with simple, low cost laser diode. The capabilities of the extensometers are presented on the example of low cyclic fatigue testing of steel specimens with hold and notch.

The introduction of integrated optical chips (IOC) in laser Doppler metrology allows new types of laser Doppler setups to be constructed. An IOC, which is made of LiNbO₃ (by application of APE/annealed proton exchange technology), splits the incoming laser beam into two outgoing measurement beams to build a crossed-beam laser Doppler setup. A special modulator driving routine is applied to achieve electrooptical phase modulation in the IOC and, hence, a mutual frequency shift between the two outlet beams. The advantages of IOCs are: consistent light delivery in optical fibres - from the LD to the IOC and onto the optical head, light splitting and frequency shifting combined in one IOC, and the introduction of a new on-line signal processing routine. Phase modulation allows for a heterodyne signal processing. In terms of signal processing, the IOC modulator is an integral component of a closed-loop arrangement. The detected signal is maintainied at a constant oscillator frequency by changing the modulator frequency in the event of Doppler frequency variation (velocity). Because the setup uses an electronically isolated optical head, length measurement is insensitive to electromagnetic radiation and thermal stress.

We present in this paper a prototype silicon retina that we have realized in standard CMOS technology. It is mainly composed of a photosensitive surface on which a metal layer representing a binary image is deposited. The partially masked photosensitive surface corresponds in fact to a photodiode which is directly connected to the output of the circuit. The readout signal is thus a current which is function of the luminous flux falling on the unmasked part of the photosensitive surface. It represents the correlation between an observed image and the reference image integrated on the sensor. The spatial sensitivity as well as the response of our retina as a function of a two-dimensional shifts between the reference image and an identical image projected on the sensor have been measured and found to correspond to our expectations. In order to improve the architecture of our retina for real time pattern recognition, we have done several computer simulations. The results of these simulations will be presented as well as the new architecture of our retina.

A new device for rapid non-contact characterization of roughness spatial distribution of flat surfaces is developed. Its operational principle is based on the strong dependence on roughness of the intensity of x-rays reflected from a superpolished surface. This effect may be used to obtain a two-dimensional map of the roughness spatial distribution for flat surface with a rms. roughness height of the order of one nanometre. The key components of this device are a precision mechanical one- dimensional scanning stage, a parabolic collimator with vacuum beam path, and a temperature stabilized cooled x-ray linear detector array.

In the production of pigment-coated paper or paperboard, the method and rate of drying of the coating will significantly influence the print quality of the finished product. Improper drying during initial st sages can cause binder migration that leads to its non-uniform concentration on the surface of the coating. Such effect causes print mottle, and is a primary reason for poor print quality. The location at which binder immobilization has occurred is called the Gel Point. An on-line fiber optic sensor system has been applied to continuously monitor the location of the Gel Point. Each sensor consists of a light source, an optical fiber for delivering the radiation, two optical fibers for diffuse and specular radiation monitoring and two detectors. The ratio R between diffuse and specular signals indicates coating conditions. A system description and experimental results are presented. The Gel Point measurement system has show that is provides a sensitive measurement of the gel point location, as it is affected by machine speed, coat weight, incoming substrate moisture levels and drying energy and can predict print mottle. This provides the paper maker with a completely independent method for monitoring the coating drying process.

A new laser ultrasonic approach, the Scanning Laser Source (SLS) technique, is presented for detection of small surface-breaking defects. In this approach we do not monitor the interaction of a generated ultrasonic wave with a flaw, as in the case of traditional pitch-catch or pulse-echo methods, but rather monitor the changes in the laser generated ultrasonic signal as the source is scanned over a defect. Changes in the amplitude and frequency content of the laser-generated ultrasound are observed resulting from the changed conditions under which the ultrasound is generated over areas without and with a surface- breaking crack. These changes are quite readily detectable using existing ultrasonic detectors. The SLS system includes a fiberized portable Q-switched YAG:Nd laser, which can be combined with either convention PZT transducers or laser interferometers. Results are presented for detection fo small EDM notches and fatigue cracks on flat and curved specimens and thin plates including real structures such as an aircraft turbine disk. It is shown that the SLS technique has several advantages over the conventional pitch-catch approach, including: (i) enhanced signal-to-noise performance, (ii) detection of defects with size smaller than the ultrasonic wavelength (at least 0.125 mm length and 0.06 mm depth), (iii) ability to detect defects of various orientations with respect to the scanning direction, (iv) inspection of surfaces with complex geometry such as bore holes and turbine disk slots.

LIBS is based on atomic emission from plasma formed by laser ablation and excitation. It offers non-contacting and nearly non-destructive elemental analysis, but limited analytical accuracy. An empirical power- law calibration curve is usually required. From our work and from recent work by Gornushkin et al. this arises from self-absorption. Assuming Local Thermal Equilibrium (LTE), irradiance is found from integrals over the Voigt profile, which we compute using the complex error function. Calibration curves show a break between linear and power-law regions, with a square-root dependence at high concentrations. Irradiance depends on width of the Lorentz (pressure broadened) component, and the simple Boltzmann temperature dependence is modified. Gornushkin et al extended calibration curves into the linear region, obtaining the Voigt parameter, but more typically this region is inaccessible. Self- absorption theory should provide improved temperature measurement in the power-law region and, although absolute concentration determination requires the Lorentz width, its known temperature and pressure dependence should reduce the ad-hoc nature of calibration curves.

In-line particle holography is subject to image deterioration due to intrinsic speckle noise. The resulting reduction in the signal to noise ratio (SNR) of the replayed image can become critical for applications such as holographic particle velocimetry (HPV) and 3D visualisation of marine plankton. Work has been done to extend the mono-disperse model relevant to HPV to include poly-disperse particle fields appropriate for the visualisation of marine plankton. Continuous and discrete particle fields are both considered. It is found that random walk statistics still apply for the poly-disperse case. The speckle field is simply the summation of the individual speckle patters due to each scatter size. Therefor the characteristic speckle parameter (which encompasses particle diameter, concentration and sample depth) is alos just the summation of the individual speckle parameters. This reduces the SNR calculation to the same form as for the mono-disperse case. For the continuous situation three distributions, power, exponential and Gaussian are discussed with the resulting SNR calcuated. The work presented here was performed as part of the Holomar project to produce a working underwater holographic camera for recording plankton.

In this paper, a contractless, all-optical and non-destructive method for separating the minority carrier recombination lifetime and surface recombination velocities on assymetrical silicon samples (that is with different surface recombination velocities on the front and back surface) at low injection level is presented. The technique can be described as a pump-probe method where the excess carrier density is probed by analyzing free carrier absorption transient following excitation pulses having several wavelengths. A novel theoretical approach to evaluate the recombinative parameters is extensively analyzed and numerical simulations, which validate the proposed methodology, are presented.

Many mechanical processes occur in microscopic timescales, therefore to visualise these developing reactions requires an imaging system that can dissect the event and provide a spatial and temporally resolved record that allows critical interrogation. Research projects are subject to intense scrutiny to contain costs, consequently high speed imaging needs to provide fast results from which reliable quantitative data can be extracted. Secondary to this are the expectations of the research community to access recorded data, without recourse to what is often regarded as out dated procedures in the subdued lighting conditions of photographic darkrooms, and exposure to environmentally dammaging chemicals. Converting an analogue image to a digital record that can be interrogated by computer can be time consuming and often suppresses fine detail. Often relatively slow mechanical events can generate a phenomenon which propagates at velocities that are orders of magnitude faster than the initial stimulus. The propagation speed of mechanically generated damage through a material is dependent on its composition, therefore to capture these fast transient events requires a versatile imaging system that can be readily programmed to satisfy a wide range of experimental conditions. A typical example of these differences can be demonstrated by crack propagation in ceramics. The initial stimulus may have a velocity of a few hundred metres per second, but the rate at which these cracks and shockwaves propagate through the material are measured in kilometres per second. The high quality images that can be captured using the Imacon 200 will facilitate a greater visual understanding of the fast phenomena that influence materials failure. Analysis functions that form an integral part of the operating software can provide quantitative results within minutes of image capture using the system computer.

We will present an overview of the different polymer/liquid crystal micro-composites and their uses for the control of the optical flux. The preparation method is the key element of this generic family of materials. There is a great number of pertinent parameters (relative concentration of constituents, irradiation conditions, ...) Acting on the morphology and therefore on the final properties. Materials with very different electro-optical properties can be obtained. We will discuss the case where the spatial repartition of heterogeneity is uniform in the sample: light occlusion films (with direct or reverse mode, selective reflection films, films with optical bistability). The cholesteric films will be particularly emphasized. We will focus on the relation between the preparation, the electro-optical properties and the colorimetric properties of the films. Next, the effect of introducing a gradient in some parameters (as irradiation, ...) influencing the material will be discussed. The use of these electrically controllable materials in adaptive optical materials for some applications such as optical components, smart windows, laser protection... will be reviewed.

The spectacular growth in MOEMS interest is highlighted by the involvement of R&D centres and industrial companies. A lot of application fields offer large opportunities for Micro-Opto-Electro- Mechanical Systems (MOEMS): optical communications (switches, cross- connect matrix, DWDM systems ...), digital image processing, adaptive optics... but also industrial maintenance, environment, medicine,... After general ideas on MEMS and MOEMS, this paper presents the main application fields for MOEMS and a few outstanding devices are presented to illustrate the recent developments. Then the work of LETI in MOEMS is presented. Some devices are fabrication with MEMS technologies such as tunable Fabry-Perot interferometers for DWDM telecommunications or 2D micro-scanners for obstacle detection. But a more specific technology has also been developed by LETI, resulting in devices made of silica such as 1D micro-scanners for obstacle detection. Moreover some devices are constituted of micro-mechanical structures combined with Integrated Optics: micro-switches for protection applications and network reconfiguration in optical communications, micro-vibration sensor for surveillance of rotating machines in electrical generators.