Multi-mode interferometric measurement system based on wavelength modulation and active vibration resistance.

We present the definition and development of a three dimensional high precision measurement system for localisation and control of machine tool's drill based on a Michelson-Morley interferometric configuration and a laser tracking subsystem to redirect the measurement beam onto a retro-reflector positioned in the tool nearness. The system measures the retro-reflector position in real time with 5 microns accuracy up to 2 m/s processing material velocities and it is used to carry out an on-line control feedback of the drill position in the machine tool allowing a drill tool replacement during the fabrication process. The system has been integrated and tested in an especially designed machine tool built for this application.

The surface flatness and the uniformity in thickness and refractive index of a mask-blank glass have been requested in semiconductor industry. The absolute optical thickness of a mask-blank glass of seven-inch square and 3mm thickness was measured by three-surface interferom etry in a wavelength tuning Fizeau interferometer. Wavelength-tuning interferometry can separate in freq uency space the three interference signals of the surface shape and the optical thickness. The wavelength of a tunable laser diode source was scanned linearly from 632 nm to 642 nm and a CCD detector recorded two thousand interference images. The number of phase variation of the interference fringes during the wavelength scanning was counted by a temporal discrete Fourier transform. The initial and final phases of the interferograms before and after the scanning were measured by a phase shifting technique with fine tunings of the wavelengths at 632 nm and 642 nm. The optical thickness defined by the group refractive index at the central wavelength of 337 nm can be measured by this technique. Experimental results show that the cross talk in multiple-surface interferometry caused a systematic error of 2.0 microns in the measured optical thickness. Keywords: Phase measurement, absolute optical path difference, wavelength scanning, optical thickness distribution measurement, phase shift, Fizeau interferometer

Optical interferometry plays an important role in the topographical surface measurement and characterization in precision/ultra-precision manufacturing. An appropriate surface reconstruction algorithm is essential in obtaining accurate topography information from the digitized interferograms. However, the performance of a surface reconstruction algorithm in interferometric measurements is influenced by environmental disturbances and system noise. This paper presents a comparative analysis of three algorithms commonly used for coherence envelope detection in vertical scanning interferometry, including the centroid method, fast Fourier transform (FFT), and Hilbert transform (HT). Numerical analysis and experimental studies were carried out to evaluate the performance of different envelope detection algorithms in terms of measurement accuracy, speed, and noise resistance. Step height standards were measured using a developed interferometer and the step profiles were reconstructed by different algorithms. The results show that the centroid method has a higher measurement speed than the FFT and HT methods, but it can only provide acceptable measurement accuracy at a low noise level. The FFT and HT methods outperform the centroid method in terms of noise immunity and measurement accuracy. Even if the FFT and HT methods provide similar measurement accuracy, the HT method has a superior measurement speed compared to the FFT method.

As single measurement method cannot fully meet the technical requirements of dust concentration measurement, the multi-mode detection method is put forward, as well as the new requirements for data processing. This paper presents a new dust concentration measurement system which contains MEMS ultrasonic sensor and MEMS capacitance sensor, and presents a new data fusion algorithm for this multi-mode dust concentration measurement system. After analyzing the relation between the data of the composite measurement method, the data fusion algorithm based on Kalman filtering is established, which effectively improve the measurement accuracy, and ultimately forms a rapid data fusion model of dust concentration measurement. Test results show that the data fusion algorithm is able to realize the rapid and exact concentration detection.

Noise pollution in urban areas is a subject of grave concern and it is being recognized globally in different countries and cities. People are facing many health-related problems because of this. Therefore, in the proposed work, we envisioned to tackle the challenge of acquiring real time and spatially fine-grained noise pollution data with a community-driven sensing infrastructure. Mobile crowdsourcing over smartphones presents a new paradigm for collecting context aware sensing data of a vast area like a city. Thus, the proposed system exploits the power of mobile crowdsourcing. The proposed system monitors the present noise level in the surroundings of the user and also generates city's noise pollution footprints. The noise map reflects the real-time pollution scenario of the city which changes with time. The prototype of the system has been evaluated with extensive experiments based on crowdsourced sensing data collected by volunteers in Kolkata city.

An elliptical motion in the torsion coupler of an oscillator‐type ultrasonic motor has been observed noninvasively by means of an optical heterodyne interferometer. Studies of the elliptical motion in the torsion coupler are important for the research on improvement of the efficiency and optimum design of an ultrasonic motor. However, to date, only microscope observation has been carried out and hence accuracy is not as high as desired. In this paper, an optical heterodyne interferometer based on a frequency‐stabilized transverse Zeeman laser is used for detection of the Doppler shift frequency by an ultrasonic vibration so that the vibration waveform of the torsion coupler has been regenerated. The oscillations of the rotor contact plane and side plane of the end of the beam have been measured individually by an identical optical system. From their amplitudes and the phases, the elliptical loci have been computed. In another method, the oscillations of the two surfaces have been measured simultaneously with two interferometer systems and their elliptical relations have been displayed in real time on an XY oscilloscope. Oscillations at each point on the beam and the variations of the elliptical shape versus the driving frequency of the ultrasonic motor have been observed successfully by the second method.

We present an algorithm in the Conformal Geometric Algebra framework which computes the transformation (rotation and translation) relating the coordinate system of an endoscopic camera, with the coordinate system of the markers placed on it. Such markers are placed in order to track the camera’s position in real time by using an optical tracking system. The problem is an adaptation of the so-called hand-eye calibration, well known in robotics; however we name it the endoscope-tracking system calibration. By this way, we can relate the preoperative data (3D model and planing of the surgery), with the data acquired in real time during the surgery by means of the optical tracking system and the endoscope. Results obtained with our approach are compared with other approach which computes separately (in a two-step algorithm) the rotation and translation, and they are promising.

Mobile applications tend to ask for users’ location in order to improve the service they provide. However, aside from increasing their service utility, they may also store these data, analyze them or share them with external parties. These privacy threats for users are a hot topic of research, leading to the development of so called Location Privacy Protection Mechanisms. LPPMs often are configurable algorithms that enable the tuning of the privacy protection they provide and thus the leveraging of the service utility. However, they usually do not provide ways to measure the achieved privacy in practice for all users of mobile devices, and even less clues on how a given configuration will impact privacy of the data given the specificities of everyone’s mobility. Moreover, as most Location Based Services require the user position in real time, these measures and predictions should be achieved in real time. In this paper we present a metric to evaluate privacy of obfuscated data based on users’ points of interest as well as a predictive model of the impact of a LPPM on these measure; both working in a real time fashion. The evaluation of the paper’s contributions is done using the state of the art LPPM Geo-I on synthetic mobility data generated to be representative of real-life users’ movements. Results highlight the relevance of the metric to capture privacy, the fitting of the model to experimental data, and the feasibility of the on-line mechanisms due to their low computing complexity.

Problem statement. Ultra-wideband real-time local positioning systems use pulsed radio signals with an effective spectrum width of at least 500 MHz for data transmission. They feature high localization accuracy (10–30 cm) and transmission speeds (up to 27.24 Mbps, with potential for growth to 480 Mbps). This makes them an essential component in building multi-purpose systems for monitoring the movements of people and vehicles, access control (without barriers), including access to hazardous areas, etc. However, the range of such systems rapidly decreases with increasing bit rate and is also dependent on many other factors. At the same time, a universal system must be fast enough to solve problems such as vehicle collision avoidance, robot control, etc. Under these conditions, the successful application of ultra-wideband solutions requires an operational mechanism for evaluating key system parameters depending on a host of influencing factors, such as signal spectral characteristics, equivalent isotropically radiated power (EIRP) spectral density standards, transceiver settings, permissible bit error rates, etc. All of these factors, at a given bit rate, affect the transmission range and sometimes the localization accuracy. These are key parameters, pri-marily for design, so their rapid evaluation under various combinations of influencing factors is a pressing issue. This work aims to create a mechanism for such an evaluation. The goal of the work is to study the factors influencing the key parameters of ultra-wideband local positioning systems in real time and, based on this, develop an evaluation model of the transmission process as a tool for system design and mainte-nance. Methods used: analysis of data on influencing factors, construction and superposition of a propaga-tion loss model and radio link budget models, working with a common model, and deriving patterns of key parameter changes at boundary values of the influencing factors. Novelty. A single common model systema-tizes the factors of two types of models that influence transmission range. Result. A tool for designing and maintaining ultra-wideband real-time local positioning systems has been developed, enabling prediction of their behavior under different combinations of influencing factors, in particular, ensuring maximum range at a given bit rate. Practical significance. The presented study can be used as a methodological support for classes introducing ultra-wideband real-time local positioning systems and estimating their range depend-ing on the transmission rate and other factors.

Acoustic source localization has been considered a great point of focus in order to solve a wide range of applications, including detection, tracking and even source classification. In surveillance applications there are different types of sensors used to provide many approaches to the problem of source localization. In this application we use arrays of seismic sensors which provide a reliable sensing solution to the problem of real time object tracking by analyzing the waves the object generates while it moves over the ground. The aim of this work is to provide the position in real time of an object moving over a designated area on a soccer field, using arrays of geophones connected to a dual core development kit called DIOPSIS 740, which comprises of a DSP and a microcontroller. The DSP is able to process 1 Gflops @ 1 MHz and counts with 4 stereo analog inputs suitable for this application. The geometry of the array and different algorithms used to determine the direction of arrival (DOA) were also matter of analysis in this work to finally implement a pair of uniform linear arrays and an algorithm based on time-delay estimation for the source tracking.

Unmanned Air Vehicles (UAVs) have potential strengths to be implemented in the battle fields. A major problem for UAVs is to plan an optimal trajectory path from its starting position to the target position in real time. For a path to be optimal it has to minimize: threat, path length, fuel consumption, flying time, and preserves dynamic constructs of the vehicle.

The incidence of optic neuropathy after stereotactic radiosurgery (SRS) is related to the total dose, fraction size, and treatment volume. Theoretically, fractionated SRS can decrease this risk. In this paper, we report our technique for fractionated SRS and assess its potential role in the management of tumors located adjacent to the anterior visual pathways. Since 1997, thirteen patients (median age: 50, range 21-76) with lesions in close proximity to the anterior visual pathways were treated on the CyberKnife image guided SRS system (Accuray, Inc., Sunnyvale, CA). The CyberKnife is a 6MV linear accelerator mounted on a robotic arm which can monitor and adjust to changes in the target position in real time thus eliminating skeletal frame immobilization and allowing for convenient multi-fraction SRS treatments. Magnetic Resonance Imaging (MRI) and computerized tomography (CT) imaging for treatment planning were obtained with the patients head immobilized in an aquaplast mask. After image fusion, the target and critical structures were delineated. Two to five fractions were prescribed with approximately a 24-hour interfraction interval. The patients received 25 Gy in 5 fractions (n=5), 21 Gy in 3 fractions (n=5), or 20 Gy in 2 fractions (n=3) to the 75-95% isodose line. Ten of the thirteen patients had good pretreatment vision. In nearly all instances, the volume of the optic nerve that received 80% of the prescribed dose was < 0.05 cm3. In all instances, the volume of the optic nerve that received 50% of the prescribed dose was </= 0.5 cm3. Only one patient received more than a 5 Gy daily dose to > 0.03 cm3 of optic nerve. With median follow up of 18 months (range 12 to 54), four patients have had improvement in their vision. No visual deterioration has been observed in any of the other patients. In addition, there has been no tumor progression within the treated field. Fractionated SRS using the CyberKnife is technically feasible and may decrease the risk of optic neuropathy. Greater patient accrual and longer follow up will be necessary to further determine the clinical benefit of this approach.

SummaryEffective and intelligent path planning algorithms designed for operation in a dynamic marine environment are essential for the safe operation of unmanned surface vehicles (USVs). Most of the current research deals with the ‘dynamic problem’ by basing solutions on the nonpractical assumption that each USV has a robust communication channel to obtain essential information such as position and velocity of marine vehicles. In this paper, a Kalman filter‐based predictive path planning algorithm is proposed. The algorithm has been designed to predict the trajectories of moving ships, and the USV's own position in real time and accordingly assesses collision risk. For path planning, a weighted fast marching square method is proposed and developed to search for the optimal path. The path can be optimised for mission requirements such as minimum distance to travel and the most safety path by adjusting weighting parameters. The proposed algorithm has been validated using a number of simulations that include practical environmental aspects. The results show that the algorithms can sufficiently deal with complex traffic environments and that the generated practical path is suited for both unmanned and manned vessels. Copyright © 2015 John Wiley &amp; Sons, Ltd.

This manuscript considers a team of Unmanned Underwater Vehicles (UUVs) such that each UUV measures the arrival time of sound signal generated from the evader. The purpose of the UUV team is to intercept the underwater evader based on the arrival time measurements. We present both the motion control for the UUV team and the algorithm to estimate the evader position in real time. In this manuscript, the UUVs chase the evader while preserving a 3D spherical formation. Moreover, the formation size is controlled adaptively to assure the convergence of the evader estimation. Our tracking approach doesn't require global localization of every UUV. The proposed approach only requires that the central UUV measures the relative position of any other UUV using proximity sensors. Simulations are utilized to verify the effectiveness of the proposed method.

Degraded transfer of memories between the visual hemifields in normal macaques revealed by a novel infrared eyetracking method without head fixation