Here we report application of imaging interferometry to the study of nanomechanical motion in biosensors and living biological systems. Using strobed interferometric microscopy we are able to probe the dynamic behavior of individual (100 x 500 x 1 micron) cantilevers in an eight cantilever array over frequencies from 0 - 1 MHz. In a related approach, we have developed an interferometric method to measure cell-specific mechanical signals in real time. This yields real-time diagnostic information about cell structure, metabolism and movement, along with response to chemical and physical stimuli. Our new approach makes use of "nanomirrors" fixed to the cell membrane. These mirrors act as nanoscopic displacement probes and can be interrogated, rapidly, by optical profiling metrology.

Shack-Hartmann sensors are commonly used wavefront sensors in a large field of applications, like adaptive optics, beam characterization and non-contact measurements. They are popular because of the ease of use and the robustness of the sensor. We introduce a new way to improve the performance of miniaturized and mass-producible optical wavefront sensors for industrial inspection: A sensor design due to an aperiodic diffractive element working as microlens array allows the use of small and cost-efficient detector chips. The diffractive element was optimized using raytracing and thin element approximation (done in Zemax). As an example, we present the design and realization of a sensor for laboratory use with a measurement diameter of 20mm. We show an example measurement and results concerning dynamic range. The measurement accuracy was determined by measuring spherical waves.

The lower limit of size measurement with PDA is about 150nm particle diameter, because of the small scattering efficiencies under this size. A model-based signal processing method is developed to determine the particle size from the autocorrelation function constructed in photon counting LDA systems by simulating the whole scattering and detecting process. An optimization algorithm is proposed to fit the computed autocorrelation function to the measured one. The errors of this signal processing method are discussed.

We demonstrate that refractive index profile of microstructure could be correctly recovered in multiwavelenght digital holographic microscope when chromatic aberration is taken into account. The chromatic aberration introduced by the optical imaging components can be can be numerically compensated in the reconstruction process. The compensation approach requires the control of the reconstructed pixel size in the image plane if a Fresnel Transformation Method is adopted to take into account the different wavelengths used to investigate the samples. Description of the method and several examples of application will be discussed.

The TTM objective module was designed to allow interferometric measurement of objects underneath transmissive materials at higher magnifications. For proper functioning, many factors must be optimized, including dispersive compensation, coherence effects, thickness variation insensitivity, and illumination. Measurement results will be presented for through glass, through fluid and dynamic MEMS application examples.

In this paper a lensless in-line digital holographic microscope is presented as interferometric applications for dynamic measurements. A diverging beam is used to illuminate the object to get the required magnification. In particular, time average in-line digital holographic interferometry is studied for vibration measurements of a smaller membrane. The sensitivities of the numerically reconstructed amplitude and phase information are studied with the distance from object to the CCD, during hologram recording. It is shown that, the increase in object recording distance results the increase in the sensitivity of the Bessel type of fringes representing the vibration amplitude information, while it shows the opposite behaviour for phase information which represent the mean deformation fringes. To explain this phenomenon, the samplings of the interference of object and reference beams, and of the diffracted speckled wavefront from the object are individually studied. A double exposure approach is used for the suppression of noise from real image wave caused by zero-order term and twin image waves because of in-line geometry. The experiment is performed for the study of vibration behaviour of harmonically excited aluminium membranes of 5 mm in size and results are presented.

This paper introduces a novel optical method to measure liquid penetration into porous, highly scattering media. Testing was conducted by measuring the sorption of glycerol into a paper sample consisting of cellulose fibre tissue with a grammage of 115 g m^-2. During wetting, optical coherence tomography (OCT) was used to detect dynamical changes in the sample's scattering properties. Distinguishing the border between the dry and the wetted area on the basis of separate A-scans was a challenging task. However, wetting behaviour could be investigated in the depth direction simply by constructing a composite image of the separate scans. In addition, the method also allowed the imaging of swelling behaviour in paper.

This study presents static and dynamic characterisation by Twyman Green interferometry of two active MEMS actuators driven by a thin film transducer of aluminium nitride (AlN). Firstly, we report on the testing results of thin film AlN/Si piezoelectric micro-machined ultrasonic transducers. These devices are expected to exhibit sensing capabilities for monitoring fluid property changes. The goal of second case study is the development of reliable AlN driven cantilevers working as actuation elements in Micro-Electro-Mechanical Systems (MEMS).

In atomic probe microscopy, micro-probes of various sizes, geometries, and materials are used to define the interface between the samples under investigation and the measuring detectors and instrumentation. Therefore, measuring resolution in atomic probe microscopy is highly dependent on the transfer function characterizing the micro-probes used. In this paper, characterization of the dynamic transfer function of specific micro-cantilever probes used in an Atomic Force Microscope (AFM) operating in the tapping mode is presented. Characterization is based on the combined application of laser Doppler vibrometry (LDV) and real-time stroboscopic optoelectronic holographic microscopy (OEHM) methodologies. LDV is used for the rapid measurement of the frequency response of the probes due to an excitation function containing multiple frequency components. Data obtained from the measured frequency response is used to identify the principal harmonics. In order to identify mode shapes corresponding to the harmonics, full-field of view OEHM is applied. This is accomplished by measurements of motion at various points on the excitation curve surrounding the identified harmonics. It is shown that the combined application of LDV and OEHM enables the high-resolution characterization of mode shapes of vibration, damping characteristics, as well as transient response of the micro-cantilever probes. Such characterization is necessary in high-resolution AFM measurements.

A heterodyne interferometer with picometer sensitivity for non-destructive characterization of micro- and nanostructures has been built. The setup is designed to measure phase and amplitude in the entire frequency range 0-1.2GHz. The object can be scanned in the x- and y-direction with sub-micrometer precision. Absolute amplitude of vibration is determined by combining separate measurements of the carrier and sideband frequency of the detected signal. The detector signal is mixed with a signal from a generator. By adjusting the frequency of the signal generator, we can choose the carrier or sideband frequency. We have performed measurements on capacitor micro-machined ultrasound transducers (CMUTs) which are being developed for diagnostic imaging of vulnerable plaques in arteries. Arrays of ~7500 CMUTs with a total area of 1.3mm x 0.9mm are planned used in an intravascular catheter. The CMUTs studied have typical radii of 5.7-12.5μm, membrane thickness of 100nm, and center frequencies 10-35MHz. Characterization of both single and arrays of CMUTs is important to optimize the manufacturing process and the design. Quality control during manufacture is also important to identify imperfect elements. Other structures have been characterized such as a piezoelectric element with excitation frequencies from a few kHz to several hundreds of kHz and a LiNbO₃ surface acoustic wave (SAW) transducer with excitation frequencies from 20MHz to 30MHz. We have performed initial measurements of absolute amplitudes with picometer resolution. Theoretical calculations agree well with the measurements. The setup can be used to characterize a large range of micro- and nanostructures.

We present a new type of point-diffraction interferometer specially designed for industrial use with high immunity to external vibration encountered in the course of measurement process. The proposed interferometer uses thermally-expanded fibers instead of conventional pinholes as the point-diffraction source to obtain a high quality reference wave with an additional advantage of relatively easy alignment of optical components. Vibration desensitization is realized through a common-path configuration that allows the influence of vibration to affect both the reference and measurement waves identically so that it is subsequently cancelled out during the interference of the two waves. A spatial phase shifter is added to capture four phase-shifted interferograms simultaneously without time delay using a single camera to avoid vibration effects. Experimental results demonstrate that the proposed interferometer is capable of providing stable measurements with a level of fringe stabilization of less than 1 nanometer in a typical workshop environment equipped with no excessive ground isolation for anti-vibration.

Interrogation tools are the key to a thorough understanding of any technology. Texas Instruments' DLP^(R) Products - Digital Mirror Device is no exception to this rule. We will discuss the application of a non-destructive, through-glass interferometer system toward gaining insight to the degree of structural uniformity of a statistically significant sampling of micro-opto-electromechanical (MOEM) mirrors as used in our product line. In the course of providing this information, instrumentation details such as reliability and reproducibility of measurements obtained on this interferometer will be discussed. Additionally, the importance of this mechanical uniformity to displaying images with this spatial light modulator (SLM) will be discussed as well.

We present design of novel tool for characterization of wafer thickness and wafer topography employing fast low coherence fiber optic interferometer, which optical length of the reference arm of the interferometer is monitored by secondary long coherence length interferometer.

The ecomony scale of return for semiconductor wafers can be attributed to 2 factors i.e.1) number of systems that is crammed onto a wafer and 2) substitution of precious metal (Au) to other material for the wafer backmetal. Any of these 2 changes will be a major challenge to semiconductor wafer dicing yield. Crack die with a random order is a great myth to be dicovered. In this study, Moire Techniques is being adopted to perform the upfront analysis on the crack die to minimize the yield loss during dicing process. In this study we focus and to corellate 3 different wafers with different size (5", 6" and 8") and backmetal (bare silicon, Au and AuX). The effect of the backside metallization to the die strength has been numerically and experimentally investigated. These results obtained is being made to optimise the dicing method to obtain a homogenous stresses across the wafer.

This paper introduces a new design of a white light interferometer, suitable for measurement of inner cylindrical or quasi-cylindrical parts. A high precision 45° conical mirror is used to direct collimated light in the radial direction to the surface to be measured. The image of the measured surface, distorted by the conical mirror, is formed in the sensor plane of a digital camera. A mapping algorithm is used to reconstruct the cylindrical geometry from the distorted image. The remaining of the interferometer is quite similar to a conventional white light interferometer, where a flat reference mirror is scanned through the measurement range while an algorithm is searching for the maximum contrast position of the interference pattern. The alignment and calibration of the interferometer using a reference master piece are described and discussed. The performance evaluation of the interferometer as well as practical applications are also presented and discussed. This new configuration makes possible to measure inner surfaces in true cylindrical coordinates.

In the present work, the temperature versus thermal Ldformation (strain) with respect to time, of different coating films were studied by a non-destructive technique (NDT) known as shearography. An organic coating, i.e., ACE Premium Enamel, on a metallic alloy, i.e., a carbon steel, was investigated at a temperature range simulating the severe weather temperatures in Kuwait especially between the daylight and the night time temperatures, 20-60 °C. The investigation focused on determining the in-plane displacement of the coating, which amounts to the thermal deformation (strain) with respect to the applied temperature range. Furthermore, the investigation focused on determining the thermal expansion coefficients of coatings, the slope of the plot of the thermal deformation (strain) versus the applied temperature range. In other words, one could determine, from the decreasing value of the thermal expansion coefficients of coatings, a critical (steady state) value of the thermal expansion coefficients of coatings, in which the integrity of the coatings can be assessed with respect to time. In fact, determination of critical (steady state) value of the thermal expansion coefficients of coatings could be accomplished independent of parameters, i.e., UV exposure, Humidity, exposure to chemical species, and so on, normally are considered in conventional methods of the assessment of the integrity of coatings. In other words, with the technique of shearography, one would need only to determine the critical (steady state) value of the thermal expansion coefficients of coatings, regardless of the history of the coating, in order to assess the integrity of coatings. Furthermore, results of shearography indicate that the technique is very useful NDT method not only for determining the critical value of the thermal expansion coefficients of different coatings, but also the technique can be used as a 2D- microscope for monitoring the deformation of the coatings in real-time at a submicroscopic scale.

We have recently demonstrated the ability to measure the absolute change in optical power (focus) of a 152 mm diameter flat mirror in vacuum between room and cryogenic temperatures (133K) with a peak-to-valley measurement error of only 22nm. Such a measurement would be crucial to the verification of the focus of a cryogenic instrument during ground testing. The testing utilized a vibration-insensitive interferometer and a reference mirror maintained at room temperature located within the thermal vacuum chamber. Special considerations were taken to ensure that the reference mirror experienced low axial thermal gradients, since structural modeling indicated that axial thermal gradients and axial variation of substrate coefficient of thermal expansion are critical in maintaining flatness under cryogenic test conditions. This paper will discuss the testing equipment and methodology and the corresponding analysis and results.

The high performance optical system is generally not easy to align. Particularly, if there are off-axis optical components in the system, the alignment is a very serious problem. Many researchers have reported that using sensitivity of some Zernike coefficients is useful in alignment. However, this method has a weak point in that it generates an accurate result only when the misalignments of component are located within the range where the sensitivities of coefficients are linear to the amount of misalignment. We developed the new method which allows larger misalignment at the early stage of alignment. It is to minimize the merit function of Zernike coefficients rather than to use sensitivities of coefficients. In this paper, we analyzed the cons and pros of conventional alignment method and our own method and demonstrated the accuracy and flexibility of our method by aligning the diameter 900 mm Cassegrain type collimator. Even though there was more than 1 mm decenter error, we could align the secondary mirror to the nominal position with just two trials.

Interferometric tests of aspheres have traditionally relied on so-called "null correctors". These usually require significant time and expense to design and fabricate, and are specific to a particular asphere prescription. What's more, they are tedious to align and calibrate. Aspheres can also be tested without null correction (using a spherical wavefront), but such capability is extremely limited. A typical interferometer can acquire only a few micrometers of fourth-order aspheric departure due to high-density interference fringes. Furthermore, standard software packages do not compensate for the impact upon a non-null measurement of (i) the part's aspheric shape or (ii) the interferometer's optical aberrations. While fringe density and asphere compensation severely limit the practical utility of a non-null asphere measurement, subaperture stitching can directly address these issues. In 2004, QED Technologies introduced the Subaperture Stitching Interferometer (SSI^(R)) to automatically stitch spherical surfaces (including hemispheres). The system also boosts accuracy with in-line calibration of systematic errors. We have recently added aspheric capability, extending non-null aspheric test capability by an order of magnitude or more. As demonstrated in the past on annular zones of nearly nulled data, subaperture stitching can extend the testable aspheric departure. We present a more generally applicable and robust method of stitching non-null aspheric phase measurements. By exploiting novel compensation schemes and in-line system error calibration, our subaperture stitching system can provide significantly better accuracy and increased testable aspheric departure over an unstitched non-null test. Examples of stitched non-null tests are analyzed in this paper, and cross-tested against corresponding null tests.

Large flat mirrors can be measured by using subaperture Fizeau interferometer and stitching the data. We have implemented such a system that can efficiently and accurately measure flat mirrors several meters in diameter using a 1 meter sub-aperture instantaneous Fizeau interferometer, coupled with sophisticated analysis software. The 1-m aperture optical system uses a fused silica test plate, reflective collimator, and commercial instantaneous interferometer. Collimator errors, mapping distortion, surface errors in the test plate, and other systematic effects were measured and compensated for individual measurements. Numerous individual maps were stitched together to determine the global shape of a 2-m class flat.

Improved patient comfort and the need for better quality diagnostic information provide the motivation for new sensor development for the urinary tract. Optical sensors based on single mode fibre optics offer unique advantages in terms of access and miniaturization. We report the design, manufacture and evaluation of a diaphragm based sensor to give better than 10 mbar pressure sensitivity. The diaphragm is formed from a medically compatible material and it's geometric parameters set to give the desired resolution. The rear surface of the diaphragm has a thin aluminum coating such that an interference signal can be detected between the light reflected from the diaphragm and the distal end of the fibre. A number of approaches have been investigated for the analysis of the signal from the sensor using broadband illumination where minimizing overall system cost has been a major driver as well as achieving the required performance. A comparison of the techniques is given and experimental data presented with validation of sensor deflection from a white light interferometer.

Digital holographic technique has been applied to analyze the spatial distribution of polarization state of light transmitted through anisotropic objects by successive hologram recording using polarization switching of the reference wave by an optical fiber Faraday rotator. For a test object, a quarter wave plate (QWP) is used and the distribution of polarization ellipse over its field is analyzed for various azimuth of the QWP. By inserting a polarizer into a part of the object wave as a reference area, a phase drift of the reference waves caused by polarization switching and environmental disturbances can be estimated and compensated for by using the phase of the known polarization area. The principal axis and ellipticity are calculated and compared with their theoretical values. A good agreement between the experimental and theoretical values is observed. For an application, a photoelastic effect induced in a compressed PMMA specimen is also investigated.

A simple method for determination of refractive index of liquids is demonstrated by using digital holographic interferometry. Number of experiments is performed to measure the refractive indices of liquid samples. Experimental results reveal that the deviation in refractive index measured by this method and that measured by Abbe refractometer are within experimental limits.

A number of deflectometric devices have been developed and built for measuring optical surfaces for industrial and research applications. hese include the scanning facility for the highly accurate and traceable measurement of large near-flat and slightly curved optical surfaces at PTB which is based on the Extended Shear Angle Difference (ESAD) deflectometry technique. ESAD combines deflectometric and shearing techniques in a unique way to enable error minimization and traceability. With this facility, sub-nm repeatability, reproducibility, and uncertainty of topography measurement have been achieved. A central optical element of the ESAD device and of several other deflectometric scanning systems is a pentagon prism which is used to deflect the light beam of an angle measuring device by 90 degrees. With ESAD, the pentagon prism is used to provide the lateral displacement of the measuring beam on the surface of the specimen to perform the shearing (angle difference) measurements, while other deflectometric systems make use of the pentagon prisms to scan the surface under test directly. It will be reported on the ESAD device using optimized opto-mechanical components, and on measurement results. Information on the adjustment of the pentagon prism, the specimen under test, and the axes of the autocollimator which has been achieved with the ESAD device will be presented. It will be reported on the reduction of the systematic errors in the angle difference measurement down to the milliarcsec level. Measurement comparisons involving ESAD deflectometry, an independent deflectometric scanning system, Fizeau interferometry using a mercury mirror, and absolute interferometry applying the skip flat method will be presented. Information on the autocollimator used as an angle measuring device and its calibration will be provided.

We describe a novel interferometric scheme that attempts to measure the absolute distance of a three-dimensionally moving target with respect to a reference station. The target transmits two orthogonal pairs of lateral-shearing interferograms generated using four near-perfect spherical waves emitted from single-mode fibers by means of point diffraction. The interferograms are modulated with varying amounts of phase shifting and monitored by the reference station holding a 2-D array of photodetectors. Captured interferograms are analyzed by use of a modified version of the Rimmer-Wyant technique and reconstructed as the spherical wavefront emitted form the center of four fibers in the target. The absolute distance of the target is then determined by fitting the reconstructed wavefront into Zernike polynomials. Experimental results are discussed to verify that the proposed method is capable of measuring the absolute distance along not only the optical axis, but also out of the axis.

In the paper we present the method for 3D measurement of birefringence in photonics components by means of automated photoelasticity combined with tomography. The enhanced measurement procedure is described and the experimental results obtained for an exotic phase object, namely glass capillary infilled with liquid crystals are presented. The sources of errors are discussed for the cases of different object models and the numerical experiments aiming in determination of limitations of the experimental procedures are performed. Finally the possibility of reduction of these errors by an introduction of additional numerical focusing priori the tomographic reconstruction algorithmis shown and its applicability is proven by numerical simulations.

We present experimental results in deformation measurement and thickness change in polymer films employing Fourier domain interferometry. The set-up is a Michelson configuration in which interference signal betweeen light reflected from a reference arm is superposed with two reflection from the first and second interface from the film sample. Distance measurements for determination of deformation and thickness values were obtained after an inverse Fourier transform of the spectrum signal. With this configuration, measurements with 1 micron axial resolution, and 2mm dynamic range were obtained.

Multipoint Diffraction Strain Sensor has been developed based on a normal moire interferometer, with the novel feature of whole field strain determination, along with the possibility of rotation and tilt determination. This unique feature has been implemented by simultaneous tracking of sampled wavefront diffracted from the component under test. In this sensor a high-frequency diffraction grating is bonded on the specimen, which is illuminated by two symmetric collimated laser beams, as in a typical moire interferometer. The first orders of diffracted beams impinge on a CCD camera, via a microlens array. The lens array serves a dual purpose - to sample the diffracted wavefront and to focus the wavefront to a number of spots on the CCD. The deviation of the individual spots generated by both of the beams is directly proportional to the normal strain and a component of the shear strain. Simultaneous strain measurement at more than a thousand points can be readily obtained and is demonstrated. This novel technique is expected to be very valuable in numerous industrial metrology applications.

Several versions of grating interferometers (GI) with conjugated wavefronts, specially adopted for in-plane displacement measurements of microelements or microregions at larger specimens, have been proposed including four-beam three mirror GI, Czarnek's interferometer or fiber optics based GI. Recently the grating interferometers based on the concept of guiding the light in a waveguide (block of glass) have been developed. Such design is especially useful to combine the measurement module with optical microscope. In the paper, we propose two versions of new compact, sensor-like optical microextensometers based on the waveguide grating interferometry. The microextensometers consist of the interferometer head integrated with illumination and detection modules, so that it can work without any microscope. The compact and portable design (using the wire-less CCD camera) enables to use it outside the laboratory, e.g. directly on the engineering objects under test. The two GI versions are devoted to: periodical measurements and constant monitoring of a reference (DOE) structure attached to an object. In the paper the concept and design of both sensors is presented together with selected numerical simulations of waveguide plate.

Preliminary results of optical diagnostics of bow shocks in a supersonic wind tunnel by applying dual-hologram shear interferometry technique are discussed. A strong refraction effect of the probing beam penetrating a region in the vicinity of a bow shock over a blunt nose cone model has been discovered. On a signal hologram the effect leads to the disappearance of holographic fringes in a narrow region attached to the shock wave front. A reconstructed interferogram in this region, being illuminated only by the comparison wave, manifests the absent of an interference pattern. Computer simulations were performed for a part of the probing beam penetrating the area of high-density steep-gradients of compressed air attaching to the central part of the shock front of a bow shock. The compressed area was modeled as a hyperbolic cap. The bow shock was assumed axisymmetric. The simulations made it possible to determine angles of deflections and found conformity with reconstructed interferograms (shadowgraph). It is concluded that in the above indicated region of bow shocks probing light is deviated refractively into some angles, which could be large enough for light rays to be blocked out and never arrive at detector (photo film). In the case, when interferometric fringes disappear the effect of strong refraction makes it impossible measuring of air density gradients in some critical region.

In this paper, a simple method for measuring current-induced frequency modulation characteristics of semiconductor lasers is reported. In this method, no complicated optical and measuring system is needed and is easy for practical application. The experimental results in low modulation frequency range show 0.2% in accuracy is achieved and the system is fit for measuring the current-induced frequency modulation characteristics of semiconductor lasers.

We demonstrated a down-hole seismic survey system that can be applied in three dimensions vertical seismic profile (VSP) detection in petroleum exploration. The results of experiments show that the system has a dynamic measurement range of 80db (ratio of maximum to minimum value) and the total delay for signal collection, process and communication is less than 200ms @ 2k bit sample rates. An array consisting of six fiber-optic accelerometers (receivers) is applied in this system. Each receiver is comprised of three fiber-optic Michelson interferometers. In order to meet the requirements of high precision and real-time measurement, the high-speed DSP chips are employed to realize the algorithms of signal filters and Phase Generated Carrier (PGC) demodulation to obtain the seismic information. Multi-ARM CPUs are introduced into the system to design the fiber-optic accelerometer array controller and the receiver array local bus that are used for real-time data communication between the multi-level receivers and controller. The system interface for traditional ELIS Down-hole Instrument Bus (EDIB) is designed by the use of FPGA so that our system can attach to EDIB and cooperate with other instruments. The design and experiments of the system are given in this paper in detail.

In order to obtain the two dimensional distribution of the refractive index changes due to the domain inversion in the RuO₂:LiNbO₃ crystal, we make use of the Mach-Zehnder interferometer system to record holograms, with the object light transmitting through the poling RuO₂:LiNbO₃ crystal, and then filter the spectrum in the frequency domain to get the object light spectrum for numerically reconstructing the object wavefront. The results confirm that the electro-chromic effect region well agrees with the domain inversion region in RuO₂:LiNbO₃ crystal.

The ESA/NASA joint space mission LISA (Laser Interferometer Space Antenna), which is planned to be launched around 2015, aims at detecting gravitational waves in the frequency band 3*10-5 Hz to 1 Hz. It consists of three satellites which form an equilateral triangle in space, representing a Michelson-interferometer with an armlength of ~ 5 million kilometer. The end mirrors of the interferometer are realized by free flying proof masses. In the current baseline design--the so-called "strap-down" architecture--the laser light coming from the distant spacecraft is not reflected by the proof mass, but the beat signal with the local oscillator is measured on the optical bench. In addition, the distance between optical bench and its associated proof mass has to be measured with the same sensitivity as in the distant spacecraft interferometer, i. e. below 10 pm/sqrt(Hz) for the translation measurement (for frequencies above 2.8*10-3 Hz with an f-2 relaxation down to 3*10-5 Hz) and below 20 nrad/sqrt(Hz) for the tilt measurement (for frequencies above 10-4 Hz with an f-1 relaxation down to 3*10-5 Hz). Here, we present a compact setup of a heterodyne interferometer which serves as a demonstrator for an optical readout for the LISA proof mass position. We measured initial noise levels below 1 nm/sqrt(Hz) and 1 urad/sqrt(Hz), respectively, for frequencies > 10-3 Hz.

Many scanning probe microscopes (SPMs) are used as image acquisition tools in such industries as microelectronics, micromechanics, lithography and biotechnology. Conventional SPMs use piezoelectric actuators in order to move either the sample or the probe. The voltage across the piezos is taken as a position indicator. However, it is known that piezos suffer from hysteresis, and from time- and temperature-dependent creep. A solution to this problem is provided by accurate, traceable measurement of the cantilever position. An exact dimensional measurement can only take place via direct comparison with a well-known reference. The traceability of the SPM can be achieved using an interferometer, traceable to the 633 nm wavelength of the He-Ne laser. For accurate measurements the position of the cantilever must be measured in addition to the torsion and bending. This article shows the basic SPM principle as well as the addition of a cantilever position detection system. This system has been realized with a special interferometer with a quadrant diode to detect the cantilever torsion and bending. The measuring beam is focused on the cantilever backside using a lens. The reflected laser beam is split and evaluated; one part of the beam is used for the interferometrical position measurement with the other part focused onto a quadrant diode. Due to the structure of the interferometrical SPM, it can be installed in many different positioning systems with large measuring ranges, including a nanopositioning and nanomeasuring machine (NPM machine), developed at the Institute of Process Measurement and Sensor Technology of the Technische Universitaet Ilmenau.

This article is about some results of the research for increasing the phase-shift sensitivity of fiber-optic hydrophone. Many factors that affect the sensitivity are discussed, including the structure of the hydrophone sensor, the substrate of the fiber and the composite structure of the fiber. The framework of the hydrophone sensor is enwound by the fiber of the reference arm of the interferometer; out of this an inner lining is used with the fiber of the signal arm enwound on it. The fiber has a composite structure. From inner to exterior there are the core, the cladding and the substrate. The thickness of the substrate has an effect on the phase-shift sensitivity of the hydrophone. Outside the sensor we spread a kind of elastic material that is sound non-transparent. This material can protect the fiber of the signal arm. It can also be regarded as the substrate of the fiber, so the thickness of the material can affect the phase-shift sensitivity of the hydrophone. The theory analysis and the experiment measurement have been made in detail in this article. And the result is that 1mm of Teflon can raise the phase-shift sensitivity by 10dBrad/Pa.

This paper presents an overview of patents and patent applications on holographic interferometry, and highlights the possibilities offered by patent searching and analysis. Thousands of patent documents relevant to holographic interferometry were uncovered by the study. The search was performed in the following databases: U.S. Patent Office, European Patent Office, Japanese Patent Office and Korean Patent Office for the time frame from 1971 through May 2006. The patent analysis unveils trends in patent temporal distribution, patent families formation, significant technological coverage within the market of system that employ holographic interferometry and other interesting insights.