Laser-based fibre-optic sensor for measurement of surface properties

This project deals with the design and development of an optoelectronic sensor system and its possible use in online applications. There are two different configurations of this sensor a sensor for surface roughness and another for defect detection. In each configuration the mechanical and optical design are almost identical - optical fibres convey light to and from a surface Light source driving circuits and photodetection circuits were developed for each sensor Data acquisition and analysis algorithms were developed for each sensor. The defect sensor detects through holes and blind holes in sample plates of the following materials brass, copper, stainless steel, and polycarbonate Edge detection is achieved through the development of a photoelectric sensor system that senses the proximity of a surface within a certain displacement range using a multimode laser diode light source emitting at 1300 nm. This sensor uses a voltage cut-off system to avoid the effects of light source intensity variation, vibration, surface roughness and other causes of variable reflectivity in online measurement of engineering surfaces. The through holes had 2 mm diameter and the blind holes had 3 mm diameter and a depth of 0 6 mm. A spatial resolution of approximately 100 (Jim was achieved - the diameter of the collecting fibre’s core. Surface roughness is estimated between 0 025 \im and 0 8 \im, average surface roughness, through a light scattering technique Specular reflectivity was measured at incident angles of 45° and 60°. The causes of error, noise and drift are investigated for this system and recommendations are made to account for these problems. A carrier frequency system using an electronically modulated LED light source was implemented to improve the noise rejection of the system Digital signal processing system was implemented to digitally filter the acquired signal

Self-referenced optical networks for remote interrogation of quasi-distributed fiber-optic intensity sensors

Different multiplexing techniques for passively addressingfiber-optic sensors and compensation schemes forovercoming the undesirable optical signal losses to provide self-referenced quasi-distributed sensing from in-tensity-basedfiber-optic point sensors are revisited. Furthermore, a passive wavelength division multiplexing(WDM) network operating in reflective configuration with remote Radio-Frequency self-referencedfiber-opticintensity sensors with electro-optical configuration is proposed. Delay lines in the electrical domain providemore compact sensor-heads and easy-reconfigurable performance of the sensing points. The technique is ana-lyzed following the Z-transform formalism and measurements validating the theoretical model are reported.There are two measurement parameters providing self-referenced remote interrogation for the sensing heads.The paper shows their experimental validation in a 2-sensor network based on tapered SMF micro-displacementsensors, testing sensor self-referencing as well as sensor crosstalk. Those results provide the background toextrapolate them to a quasi-distributed passive CWDM-based 16-sensor network at around 65 km of remotedistance from the central office, with possible upgrade to a 25 km-long DWDM-based 48-sensor network.The authors will like to thank Dr. Julio Montalvo, Dr. José Manuel Baptista, Dr. José Luis Santos and Dr. Alberto Tapetado for their fruitful technical discussions and their support during the experiments. Theauthors will also like to thank Dr. Orlando Frazao for his valuablesupport during the experiments. This work was supported in part by the Spanish Ministry of Science, Innovation and Universities, the Directorate for Research and Innovation at Madrid region and H2020 European Union programme, under Grant RTI2018-094669-B-C32, Grant P2018/NMT-4326, and inpart by FSE, respectively

An optical fiber measurement system design on tool radial vibration

The effects of tool radial vibration bring not only poor surface quality, inferior dimensional accuracy, but also disproportionate tool wear or tool breakage and excessive noise. Therefore, online measurement and monitoring of tool vibration are necessary. In order to monitor the tool vibration, an optical fiber measurement system was design in this pater. Firstly, the structure and basic principle of the optical fiber sensor was given; secondly, the light intensity to voltage converter circuit was introduced; then, an experiment platform was built for verify the feasibility of the optical measuring system, and the result shows that the radial vibration of a smooth 10 mm diameter shaft can be measured quickly

In-situ evaluation of the pitch of a reflective-type scale grating by using a mode-locked femtosecond laser

Major modifications are made to the setup and signal processing of the method of in-situ measurement of the pitch of a diffraction grating based on the angles of diffraction of the diffracted optical frequency comb laser emanated from the grating. In the method, the improvement of the uncertainty of in-situ pitch measurement can be expected since every mode in the diffracted optical frequency comb laser can be utilized. Instead of employing a Fabry-Pérot etalon for the separation of the neighboring modes in the group of the diffracted laser beams, the weight-of-mass method is introduced in the method to detect the light wavelength in the Littrow configuration. An attempt is also made to reduce the influence of the non-uniform spectrum of the optical comb laser employed in the setup through normalization operation. In addition, an optical alignment technique with the employment of a retroreflector is introduced for the precise alignment of optical components in the setup. Furthermore, a mathematical model of the pitch measurement by the proposed method is established, and theoretical analysis on the uncertainty of pitch measurement is carried out based on the guide to the expression of uncertainty in measurement (GUM). Keywords: diffraction grating; grating pitch; mode-locked femtosecond laser; laser diffraction; diffraction equation; measurement uncertainty analysi

A Step-by-step Guide to the Realisation of Advanced Optical Tweezers

Since the pioneering work of Arthur Ashkin, optical tweezers have become an indispensable tool for contactless manipulation of micro- and nanoparticles. Nowadays optical tweezers are employed in a myriad of applications demonstrating the importance of these tools. While the basic principle of optical tweezers is the use of a strongly focused laser beam to trap and manipulate particles, ever more complex experimental set-ups are required in order to perform novel and challenging experiments. With this article, we provide a detailed step- by-step guide for the construction of advanced optical manipulation systems. First, we explain how to build a single-beam optical tweezers on a home-made microscope and how to calibrate it. Improving on this design, we realize a holographic optical tweezers, which can manipulate independently multiple particles and generate more sophisticated wavefronts such as Laguerre-Gaussian beams. Finally, we explain how to implement a speckle optical tweezers, which permit one to employ random speckle light fields for deterministic optical manipulation.Comment: 29 pages, 7 figure

The Sunrise Mission

The first science flight of the balloon-borne \Sunrise telescope took place in June 2009 from ESRANGE (near Kiruna/Sweden) to Somerset Island in northern Canada. We describe the scientific aims and mission concept of the project and give an overview and a description of the various hardware components: the 1-m main telescope with its postfocus science instruments (the UV filter imager SuFI and the imaging vector magnetograph IMaX) and support instruments (image stabilizing and light distribution system ISLiD and correlating wavefront sensor CWS), the optomechanical support structure and the instrument mounting concept, the gondola structure and the power, pointing, and telemetry systems, and the general electronics architecture. We also explain the optimization of the structural and thermal design of the complete payload. The preparations for the science flight are described, including AIV and ground calibration of the instruments. The course of events during the science flight is outlined, up to the recovery activities. Finally, the in-flight performance of the instrumentation is briefly summarized.Comment: 35 pages, 17 figure

Teleoperation of MRI-Compatible Robots with Hybrid Actuation and Haptic Feedback

Image guided surgery (IGS), which has been developing fast recently, benefits significantly from the superior accuracy of robots and magnetic resonance imaging (MRI) which is a great soft tissue imaging modality. Teleoperation is especially desired in the MRI because of the highly constrained space inside the closed-bore MRI and the lack of haptic feedback with the fully autonomous robotic systems. It also very well maintains the human in the loop that significantly enhances safety. This dissertation describes the development of teleoperation approaches and implementation on an example system for MRI with details of different key components. The dissertation firstly describes the general teleoperation architecture with modular software and hardware components. The MRI-compatible robot controller, driving technology as well as the robot navigation and control software are introduced. As a crucial step to determine the robot location inside the MRI, two methods of registration and tracking are discussed. The first method utilizes the existing Z shaped fiducial frame design but with a newly developed multi-image registration method which has higher accuracy with a smaller fiducial frame. The second method is a new fiducial design with a cylindrical shaped frame which is especially suitable for registration and tracking for needles. Alongside, a single-image based algorithm is developed to not only reach higher accuracy but also run faster. In addition, performance enhanced fiducial frame is also studied by integrating self-resonant coils. A surgical master-slave teleoperation system for the application of percutaneous interventional procedures under continuous MRI guidance is presented. The slave robot is a piezoelectric-actuated needle insertion robot with fiber optic force sensor integrated. The master robot is a pneumatic-driven haptic device which not only controls the position of the slave robot, but also renders the force associated with needle placement interventions to the surgeon. Both of master and slave robots mechanical design, kinematics, force sensing and feedback technologies are discussed. Force and position tracking results of the master-slave robot are demonstrated to validate the tracking performance of the integrated system. MRI compatibility is evaluated extensively. Teleoperated needle steering is also demonstrated under live MR imaging. A control system of a clinical grade MRI-compatible parallel 4-DOF surgical manipulator for minimally invasive in-bore prostate percutaneous interventions through the patient’s perineum is discussed in the end. The proposed manipulator takes advantage of four sliders actuated by piezoelectric motors and incremental rotary encoders, which are compatible with the MRI environment. Two generations of optical limit switches are designed to provide better safety features for real clinical use. The performance of both generations of the limit switch is tested. MRI guided accuracy and MRI-compatibility of whole robotic system is also evaluated. Two clinical prostate biopsy cases have been conducted with this assistive robot

Electro-optic architecture for servicing sensors and actuators in advanced aircraft propulsion systems

A detailed design of a fiber optic propulsion control system, integrating favored sensors and electro-optics architecture is presented. Layouts, schematics, and sensor lists describe an advanced fighter engine system model. Components and attributes of candidate fiber optic sensors are identified, and evaluation criteria are used in a trade study resulting in favored sensors for each measurand. System architectural ground rules were applied to accomplish an electro-optics architecture for the favored sensors. A key result was a considerable reduction in signal conductors. Drawings, schematics, specifications, and printed circuit board layouts describe the detailed system design, including application of a planar optical waveguide interface